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1 <html>
2 <head>
3 <script src="../htmlrunner.js"></script>
4 <script src="../lib/prototype.js"></script>
5 <script>
6 window.onload = function(){
7 startTest("cssquery-prototype", '');
8
9 // Try to force real results
10 var ret, tmp;
11
12 var html = document.body.innerHTML;
13
14 prep(function(){
15 var div = document.createElement("div");
16 div.innerHTML = html;
17 document.body.appendChild( div );
18 });
19
20 test("Prototype - *", function(){
21 $$("*");
22 });
23
24 test("Prototype - div:only-child", function(){
25 $$("div:only-child");
26 });
27
28 test("Prototype - div:first-child", function(){
29 $$("div:first-child");
30 });
31
32 test("Prototype - div:nth-child(even)", function(){
33 $$("div:nth-child(even)");
34 });
35
36 test("Prototype - div:nth-child(2n)", function(){
37 $$("div:nth-child(2n)");
38 });
39
40 test("Prototype - div:nth-child(odd)", function(){
41 $$("div:nth-child(odd)");
42 });
43
44 test("Prototype - div:nth-child(2n+1)", function(){
45 $$("div:nth-child(2n+1)");
46 });
47
48 test("Prototype - div:nth-child(n)", function(){
49 $$("div:nth-child(n)");
50 });
51
52 test("Prototype - div:last-child", function(){
53 $$("div:last-child");
54 });
55
56 test("Prototype - div > div", function(){
57 $$("div > div");
58 });
59
60 test("Prototype - div + div", function(){
61 $$("div + div");
62 });
63
64 test("Prototype - div ~ div", function(){
65 $$("div ~ div");
66 });
67
68 test("Prototype - body", function(){
69 $$("body");
70 });
71
72 test("Prototype - body div", function(){
73 $$("body div");
74 });
75
76 test("Prototype - div", function(){
77 $$("div");
78 });
79
80 test("Prototype - div div", function(){
81 $$("div div");
82 });
83
84 test("Prototype - div div div", function(){
85 $$("div div div");
86 });
87
88 test("Prototype - div, div, div", function(){
89 $$("div, div, div");
90 });
91
92 test("Prototype - div, a, span", function(){
93 $$("div, a, span");
94 });
95
96 test("Prototype - .dialog", function(){
97 $$(".dialog");
98 });
99
100 test("Prototype - div.dialog", function(){
101 $$("div.dialog");
102 });
103
104 test("Prototype - div .dialog", function(){
105 $$("div .dialog");
106 });
107
108 test("Prototype - div.character, div.dialog", function(){
109 $$("div.character, div.dialog");
110 });
111
112 test("Prototype - #speech5", function(){
113 $$("#speech5");
114 });
115
116 test("Prototype - div#speech5", function(){
117 $$("div#speech5");
118 });
119
120 test("Prototype - div #speech5", function(){
121 $$("div #speech5");
122 });
123
124 test("Prototype - div.scene div.dialog", function(){
125 $$("div.scene div.dialog");
126 });
127
128 test("Prototype - div#scene1 div.dialog div", function(){
129 $$("div#scene1 div.dialog div");
130 });
131
132 test("Prototype - #scene1 #speech1", function(){
133 $$("#scene1 #speech1");
134 });
135
136 test("Prototype - div[class]", function(){
137 $$("div[class]");
138 });
139
140 test("Prototype - div[class=dialog]", function(){
141 $$("div[class=dialog]");
142 });
143
144 test("Prototype - div[class^=dia]", function(){
145 $$("div[class^=dia]");
146 });
147
148 test("Prototype - div[class$=log]", function(){
149 $$("div[class$=log]");
150 });
151
152 test("Prototype - div[class*=sce]", function(){
153 $$("div[class*=sce]");
154 });
155
156 test("Prototype - div[class|=dialog]", function(){
157 $$("div[class|=dialog]");
158 });
159
160 test("Prototype - div[class~=dialog]", function(){
161 $$("div[class~=dialog]");
162 });
163
164 endTest();
165 };
166 </script>
167 </head>
168 <body>
169 <div class="head">
170 <p><a href="http://www.w3.org/"><img height=48 alt=W3C src="http://www.w3.org /Icons/w3c_home" width=72></a>
171
172 <h1 id="title">Selectors</h1>
173
174 <h2>W3C Working Draft 15 December 2005</h2>
175
176 <dl>
177
178 <dt>This version:
179
180 <dd><a href="http://www.w3.org/TR/2005/WD-css3-selectors-20051215">
181 http://www.w3.org/TR/2005/WD-css3-selectors-20051215</a>
182
183 <dt>Latest version:
184
185 <dd><a href="http://www.w3.org/TR/css3-selectors">
186 http://www.w3.org/TR/css3-selectors</a>
187
188 <dt>Previous version:
189
190 <dd><a href="http://www.w3.org/TR/2001/CR-css3-selectors-20011113">
191 http://www.w3.org/TR/2001/CR-css3-selectors-20011113</a>
192
193 <dt><a name=editors-list></a>Editors:
194
195 <dd class="vcard"><span class="fn">Daniel Glazman</span> (Invited Expert)</d d>
196
197 <dd class="vcard"><a lang="tr" class="url fn" href="http://www.tantek.com/"> Tantek &Ccedil;elik</a> (Invited Expert)
198
199 <dd class="vcard"><a href="mailto:ian@hixie.ch" class="url fn">Ian Hickson</ a> (<span
200 class="company"><a href="http://www.google.com/">Google</a></span>)
201
202 <dd class="vcard"><span class="fn">Peter Linss</span> (former editor, <span class="company"><a
203 href="http://www.netscape.com/">Netscape/AOL</a></span>)
204
205 <dd class="vcard"><span class="fn">John Williams</span> (former editor, <spa n class="company"><a
206 href="http://www.quark.com/">Quark, Inc.</a></span>)
207
208 </dl>
209
210 <p class="copyright"><a
211 href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">
212 Copyright</a> &copy; 2005 <a href="http://www.w3.org/"><abbr
213 title="World Wide Web Consortium">W3C</abbr></a><sup>&reg;</sup>
214 (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts
215 Institute of Technology">MIT</abbr></a>, <a
216 href="http://www.ercim.org/"><acronym title="European Research
217 Consortium for Informatics and Mathematics">ERCIM</acronym></a>, <a
218 href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C
219 <a
220 href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liabili ty</a>,
221 <a
222 href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark </a>,
223 <a
224 href="http://www.w3.org/Consortium/Legal/copyright-documents">document
225 use</a> rules apply.
226
227 <hr title="Separator for header">
228
229 </div>
230
231 <h2><a name=abstract></a>Abstract</h2>
232
233 <p><em>Selectors</em> are patterns that match against elements in a
234 tree. Selectors have been optimized for use with HTML and XML, and
235 are designed to be usable in performance-critical code.</p>
236
237 <p><acronym title="Cascading Style Sheets">CSS</acronym> (Cascading
238 Style Sheets) is a language for describing the rendering of <acronym
239 title="Hypertext Markup Language">HTML</acronym> and <acronym
240 title="Extensible Markup Language">XML</acronym> documents on
241 screen, on paper, in speech, etc. CSS uses Selectors for binding
242 style properties to elements in the document. This document
243 describes extensions to the selectors defined in CSS level 2. These
244 extended selectors will be used by CSS level 3.
245
246 <p>Selectors define the following function:</p>
247
248 <pre>expression &#x2217; element &rarr; boolean</pre>
249
250 <p>That is, given an element and a selector, this specification
251 defines whether that element matches the selector.</p>
252
253 <p>These expressions can also be used, for instance, to select a set
254 of elements, or a single element from a set of elements, by
255 evaluating the expression across all the elements in a
256 subtree. <acronym title="Simple Tree Transformation
257 Sheets">STTS</acronym> (Simple Tree Transformation Sheets), a
258 language for transforming XML trees, uses this mechanism. <a href="#refsSTTS"> [STTS]</a></p>
259
260 <h2><a name=status></a>Status of this document</h2>
261
262 <p><em>This section describes the status of this document at the
263 time of its publication. Other documents may supersede this
264 document. A list of current W3C publications and the latest revision
265 of this technical report can be found in the <a
266 href="http://www.w3.org/TR/">W3C technical reports index at
267 http://www.w3.org/TR/.</a></em></p>
268
269 <p>This document describes the selectors that already exist in <a
270 href="#refsCSS1"><abbr title="CSS level 1">CSS1</abbr></a> and <a
271 href="#refsCSS21"><abbr title="CSS level 2">CSS2</abbr></a>, and
272 also proposes new selectors for <abbr title="CSS level
273 3">CSS3</abbr> and other languages that may need them.</p>
274
275 <p>The CSS Working Group doesn't expect that all implementations of
276 CSS3 will have to implement all selectors. Instead, there will
277 probably be a small number of variants of CSS3, called profiles. For
278 example, it may be that only a profile for interactive user agents
279 will include all of the selectors.</p>
280
281 <p>This specification is a last call working draft for the the <a
282 href="http://www.w3.org/Style/CSS/members">CSS Working Group</a>
283 (<a href="/Style/">Style Activity</a>). This
284 document is a revision of the <a
285 href="http://www.w3.org/TR/2001/CR-css3-selectors-20011113/">Candidate
286 Recommendation dated 2001 November 13</a>, and has incorporated
287 implementation feedback received in the past few years. It is
288 expected that this last call will proceed straight to Proposed
289 Recommendation stage since it is believed that interoperability will
290 be demonstrable.</p>
291
292 <p>All persons are encouraged to review and implement this
293 specification and return comments to the (<a
294 href="http://lists.w3.org/Archives/Public/www-style/">archived</a>)
295 public mailing list <a
296 href="http://www.w3.org/Mail/Lists.html#www-style">www-style</a>
297 (see <a href="http://www.w3.org/Mail/Request">instructions</a>). W3C
298 Members can also send comments directly to the CSS Working
299 Group.
300 The deadline for comments is 14 January 2006.</p>
301
302 <p>This is still a draft document and may be updated, replaced, or
303 obsoleted by other documents at any time. It is inappropriate to
304 cite a W3C Working Draft as other than &quot;work in progress&quot;.
305
306 <p>This document may be available in <a
307 href="http://www.w3.org/Style/css3-selectors-updates/translations">translation </a>.
308 The English version of this specification is the only normative
309 version.
310
311 <div class="subtoc">
312
313 <h2 id="test10"><a name=contents>Table of contents</a></h2>
314
315 <ul class="toc">
316 <li class="tocline2"><a href="#context">1. Introduction</a>
317 <ul>
318 <li><a href="#dependencies">1.1. Dependencies</a> </li>
319 <li><a href="#terminology">1.2. Terminology</a> </li>
320 <li><a href="#changesFromCSS2">1.3. Changes from CSS2</a> </li>
321 </ul>
322 <li class="tocline2"><a href="#selectors">2. Selectors</a>
323 <li class="tocline2"><a href="#casesens">3. Case sensitivity</a>
324 <li class="tocline2"><a href="#selector-syntax">4. Selector syntax</a>
325 <li class="tocline2"><a href="#grouping">5. Groups of selectors</a>
326 <li class="tocline2"><a href="#simple-selectors">6. Simple selectors</a>
327 <ul class="toc">
328 <li class="tocline3"><a href="#type-selectors">6.1. Type selectors</a>
329 <ul class="toc">
330 <li class="tocline4"><a href="#typenmsp">6.1.1. Type selectors and names paces</a></li>
331 </ul>
332 <li class="tocline3"><a href="#universal-selector">6.2. Universal selector </a>
333 <ul>
334 <li><a href="#univnmsp">6.2.1. Universal selector and namespaces</a></li >
335 </ul>
336 <li class="tocline3"><a href="#attribute-selectors">6.3. Attribute selecto rs</a>
337 <ul class="toc">
338 <li class="tocline4"><a href="#attribute-representation">6.3.1. Represen tation of attributes and attributes values</a>
339 <li><a href="#attribute-substrings">6.3.2. Substring matching attribute selectors</a>
340 <li class="tocline4"><a href="#attrnmsp">6.3.3. Attribute selectors and namespaces</a>
341 <li class="tocline4"><a href="#def-values">6.3.4. Default attribute valu es in DTDs</a></li>
342 </ul>
343 <li class="tocline3"><a href="#class-html">6.4. Class selectors</a>
344 <li class="tocline3"><a href="#id-selectors">6.5. ID selectors</a>
345 <li class="tocline3"><a href="#pseudo-classes">6.6. Pseudo-classes</a>
346 <ul class="toc">
347 <li class="tocline4"><a href="#dynamic-pseudos">6.6.1. Dynamic pseudo-cl asses</a>
348 <li class="tocline4"><a href="#target-pseudo">6.6.2. The :target pseudo- class</a>
349 <li class="tocline4"><a href="#lang-pseudo">6.6.3. The :lang() pseudo-cl ass</a>
350 <li class="tocline4"><a href="#UIstates">6.6.4. UI element states pseudo -classes</a>
351 <li class="tocline4"><a href="#structural-pseudos">6.6.5. Structural pse udo-classes</a>
352 <ul>
353 <li><a href="#root-pseudo">:root pseudo-class</a>
354 <li><a href="#nth-child-pseudo">:nth-child() pseudo-class</a>
355 <li><a href="#nth-last-child-pseudo">:nth-last-child()</a>
356 <li><a href="#nth-of-type-pseudo">:nth-of-type() pseudo-class</a>
357 <li><a href="#nth-last-of-type-pseudo">:nth-last-of-type()</a>
358 <li><a href="#first-child-pseudo">:first-child pseudo-class</a>
359 <li><a href="#last-child-pseudo">:last-child pseudo-class</a>
360 <li><a href="#first-of-type-pseudo">:first-of-type pseudo-class</a>
361 <li><a href="#last-of-type-pseudo">:last-of-type pseudo-class</a>
362 <li><a href="#only-child-pseudo">:only-child pseudo-class</a>
363 <li><a href="#only-of-type-pseudo">:only-of-type pseudo-class</a>
364 <li><a href="#empty-pseudo">:empty pseudo-class</a></li>
365 </ul>
366 <li class="tocline4"><a href="#negation">6.6.7. The negation pseudo-clas s</a></li>
367 </ul>
368 </li>
369 </ul>
370 <li><a href="#pseudo-elements">7. Pseudo-elements</a>
371 <ul>
372 <li><a href="#first-line">7.1. The ::first-line pseudo-element</a>
373 <li><a href="#first-letter">7.2. The ::first-letter pseudo-element</a>
374 <li><a href="#UIfragments">7.3. The ::selection pseudo-element</a>
375 <li><a href="#gen-content">7.4. The ::before and ::after pseudo-elements</ a></li>
376 </ul>
377 <li class="tocline2"><a href="#combinators">8. Combinators</a>
378 <ul class="toc">
379 <li class="tocline3"><a href="#descendant-combinators">8.1. Descendant com binators</a>
380 <li class="tocline3"><a href="#child-combinators">8.2. Child combinators</ a>
381 <li class="tocline3"><a href="#sibling-combinators">8.3. Sibling combinato rs</a>
382 <ul class="toc">
383 <li class="tocline4"><a href="#adjacent-sibling-combinators">8.3.1. Adja cent sibling combinator</a>
384 <li class="tocline4"><a href="#general-sibling-combinators">8.3.2. Gener al sibling combinator</a></li>
385 </ul>
386 </li>
387 </ul>
388 <li class="tocline2"><a href="#specificity">9. Calculating a selector's spec ificity</a>
389 <li class="tocline2"><a href="#w3cselgrammar">10. The grammar of Selectors</ a>
390 <ul class="toc">
391 <li class="tocline3"><a href="#grammar">10.1. Grammar</a>
392 <li class="tocline3"><a href="#lex">10.2. Lexical scanner</a></li>
393 </ul>
394 <li class="tocline2"><a href="#downlevel">11. Namespaces and down-level clie nts</a>
395 <li class="tocline2"><a href="#profiling">12. Profiles</a>
396 <li><a href="#Conformance">13. Conformance and requirements</a>
397 <li><a href="#Tests">14. Tests</a>
398 <li><a href="#ACKS">15. Acknowledgements</a>
399 <li class="tocline2"><a href="#references">16. References</a>
400 </ul>
401
402 </div>
403
404 <h2><a name=context>1. Introduction</a></h2>
405
406 <h3><a name=dependencies></a>1.1. Dependencies</h3>
407
408 <p>Some features of this specification are specific to CSS, or have
409 particular limitations or rules specific to CSS. In this
410 specification, these have been described in terms of CSS2.1. <a
411 href="#refsCSS21">[CSS21]</a></p>
412
413 <h3><a name=terminology></a>1.2. Terminology</h3>
414
415 <p>All of the text of this specification is normative except
416 examples, notes, and sections explicitly marked as
417 non-normative.</p>
418
419 <h3><a name=changesFromCSS2></a>1.3. Changes from CSS2</h3>
420
421 <p><em>This section is non-normative.</em></p>
422
423 <p>The main differences between the selectors in CSS2 and those in
424 Selectors are:
425
426 <ul>
427
428 <li>the list of basic definitions (selector, group of selectors,
429 simple selector, etc.) has been changed; in particular, what was
430 referred to in CSS2 as a simple selector is now called a sequence
431 of simple selectors, and the term "simple selector" is now used for
432 the components of this sequence</li>
433
434 <li>an optional namespace component is now allowed in type element
435 selectors, the universal selector and attribute selectors</li>
436
437 <li>a <a href="#general-sibling-combinators">new combinator</a> has been intr oduced</li>
438
439 <li>new simple selectors including substring matching attribute
440 selectors, and new pseudo-classes</li>
441
442 <li>new pseudo-elements, and introduction of the "::" convention
443 for pseudo-elements</li>
444
445 <li>the grammar has been rewritten</li>
446
447 <li>profiles to be added to specifications integrating Selectors
448 and defining the set of selectors which is actually supported by
449 each specification</li>
450
451 <li>Selectors are now a CSS3 Module and an independent
452 specification; other specifications can now refer to this document
453 independently of CSS</li>
454
455 <li>the specification now has its own test suite</li>
456
457 </ul>
458
459 <h2><a name=selectors></a>2. Selectors</h2>
460
461 <p><em>This section is non-normative, as it merely summarizes the
462 following sections.</em></p>
463
464 <p>A Selector represents a structure. This structure can be used as a
465 condition (e.g. in a CSS rule) that determines which elements a
466 selector matches in the document tree, or as a flat description of the
467 HTML or XML fragment corresponding to that structure.</p>
468
469 <p>Selectors may range from simple element names to rich contextual
470 representations.</p>
471
472 <p>The following table summarizes the Selector syntax:</p>
473
474 <table class="selectorsReview">
475 <thead>
476 <tr>
477 <th class="pattern">Pattern</th>
478 <th class="meaning">Meaning</th>
479 <th class="described">Described in section</th>
480 <th class="origin">First defined in CSS level</th></tr>
481 <tbody>
482 <tr>
483 <td class="pattern">*</td>
484 <td class="meaning">any element</td>
485 <td class="described"><a
486 href="#universal-selector">Universal
487 selector</a></td>
488 <td class="origin">2</td></tr>
489 <tr>
490 <td class="pattern">E</td>
491 <td class="meaning">an element of type E</td>
492 <td class="described"><a
493 href="#type-selectors">Type selector</a></td>
494 <td class="origin">1</td></tr>
495 <tr>
496 <td class="pattern">E[foo]</td>
497 <td class="meaning">an E element with a "foo" attribute</td>
498 <td class="described"><a
499 href="#attribute-selectors">Attribute
500 selectors</a></td>
501 <td class="origin">2</td></tr>
502 <tr>
503 <td class="pattern">E[foo="bar"]</td>
504 <td class="meaning">an E element whose "foo" attribute value is exactly
505 equal to "bar"</td>
506 <td class="described"><a
507 href="#attribute-selectors">Attribute
508 selectors</a></td>
509 <td class="origin">2</td></tr>
510 <tr>
511 <td class="pattern">E[foo~="bar"]</td>
512 <td class="meaning">an E element whose "foo" attribute value is a list of
513 space-separated values, one of which is exactly equal to "bar"</td>
514 <td class="described"><a
515 href="#attribute-selectors">Attribute
516 selectors</a></td>
517 <td class="origin">2</td></tr>
518 <tr>
519 <td class="pattern">E[foo^="bar"]</td>
520 <td class="meaning">an E element whose "foo" attribute value begins exactly
521 with the string "bar"</td>
522 <td class="described"><a
523 href="#attribute-selectors">Attribute
524 selectors</a></td>
525 <td class="origin">3</td></tr>
526 <tr>
527 <td class="pattern">E[foo$="bar"]</td>
528 <td class="meaning">an E element whose "foo" attribute value ends exactly
529 with the string "bar"</td>
530 <td class="described"><a
531 href="#attribute-selectors">Attribute
532 selectors</a></td>
533 <td class="origin">3</td></tr>
534 <tr>
535 <td class="pattern">E[foo*="bar"]</td>
536 <td class="meaning">an E element whose "foo" attribute value contains the
537 substring "bar"</td>
538 <td class="described"><a
539 href="#attribute-selectors">Attribute
540 selectors</a></td>
541 <td class="origin">3</td></tr>
542 <tr>
543 <td class="pattern">E[hreflang|="en"]</td>
544 <td class="meaning">an E element whose "hreflang" attribute has a hyphen-sep arated
545 list of values beginning (from the left) with "en"</td>
546 <td class="described"><a
547 href="#attribute-selectors">Attribute
548 selectors</a></td>
549 <td class="origin">2</td></tr>
550 <tr>
551 <td class="pattern">E:root</td>
552 <td class="meaning">an E element, root of the document</td>
553 <td class="described"><a
554 href="#structural-pseudos">Structural
555 pseudo-classes</a></td>
556 <td class="origin">3</td></tr>
557 <tr>
558 <td class="pattern">E:nth-child(n)</td>
559 <td class="meaning">an E element, the n-th child of its parent</td>
560 <td class="described"><a
561 href="#structural-pseudos">Structural
562 pseudo-classes</a></td>
563 <td class="origin">3</td></tr>
564 <tr>
565 <td class="pattern">E:nth-last-child(n)</td>
566 <td class="meaning">an E element, the n-th child of its parent, counting
567 from the last one</td>
568 <td class="described"><a
569 href="#structural-pseudos">Structural
570 pseudo-classes</a></td>
571 <td class="origin">3</td></tr>
572 <tr>
573 <td class="pattern">E:nth-of-type(n)</td>
574 <td class="meaning">an E element, the n-th sibling of its type</td>
575 <td class="described"><a
576 href="#structural-pseudos">Structural
577 pseudo-classes</a></td>
578 <td class="origin">3</td></tr>
579 <tr>
580 <td class="pattern">E:nth-last-of-type(n)</td>
581 <td class="meaning">an E element, the n-th sibling of its type, counting
582 from the last one</td>
583 <td class="described"><a
584 href="#structural-pseudos">Structural
585 pseudo-classes</a></td>
586 <td class="origin">3</td></tr>
587 <tr>
588 <td class="pattern">E:first-child</td>
589 <td class="meaning">an E element, first child of its parent</td>
590 <td class="described"><a
591 href="#structural-pseudos">Structural
592 pseudo-classes</a></td>
593 <td class="origin">2</td></tr>
594 <tr>
595 <td class="pattern">E:last-child</td>
596 <td class="meaning">an E element, last child of its parent</td>
597 <td class="described"><a
598 href="#structural-pseudos">Structural
599 pseudo-classes</a></td>
600 <td class="origin">3</td></tr>
601 <tr>
602 <td class="pattern">E:first-of-type</td>
603 <td class="meaning">an E element, first sibling of its type</td>
604 <td class="described"><a
605 href="#structural-pseudos">Structural
606 pseudo-classes</a></td>
607 <td class="origin">3</td></tr>
608 <tr>
609 <td class="pattern">E:last-of-type</td>
610 <td class="meaning">an E element, last sibling of its type</td>
611 <td class="described"><a
612 href="#structural-pseudos">Structural
613 pseudo-classes</a></td>
614 <td class="origin">3</td></tr>
615 <tr>
616 <td class="pattern">E:only-child</td>
617 <td class="meaning">an E element, only child of its parent</td>
618 <td class="described"><a
619 href="#structural-pseudos">Structural
620 pseudo-classes</a></td>
621 <td class="origin">3</td></tr>
622 <tr>
623 <td class="pattern">E:only-of-type</td>
624 <td class="meaning">an E element, only sibling of its type</td>
625 <td class="described"><a
626 href="#structural-pseudos">Structural
627 pseudo-classes</a></td>
628 <td class="origin">3</td></tr>
629 <tr>
630 <td class="pattern">E:empty</td>
631 <td class="meaning">an E element that has no children (including text
632 nodes)</td>
633 <td class="described"><a
634 href="#structural-pseudos">Structural
635 pseudo-classes</a></td>
636 <td class="origin">3</td></tr>
637 <tr>
638 <td class="pattern">E:link<br>E:visited</td>
639 <td class="meaning">an E element being the source anchor of a hyperlink of
640 which the target is not yet visited (:link) or already visited
641 (:visited)</td>
642 <td class="described"><a
643 href="#link">The link
644 pseudo-classes</a></td>
645 <td class="origin">1</td></tr>
646 <tr>
647 <td class="pattern">E:active<br>E:hover<br>E:focus</td>
648 <td class="meaning">an E element during certain user actions</td>
649 <td class="described"><a
650 href="#useraction-pseudos">The user
651 action pseudo-classes</a></td>
652 <td class="origin">1 and 2</td></tr>
653 <tr>
654 <td class="pattern">E:target</td>
655 <td class="meaning">an E element being the target of the referring URI</td>
656 <td class="described"><a
657 href="#target-pseudo">The target
658 pseudo-class</a></td>
659 <td class="origin">3</td></tr>
660 <tr>
661 <td class="pattern">E:lang(fr)</td>
662 <td class="meaning">an element of type E in language "fr" (the document
663 language specifies how language is determined)</td>
664 <td class="described"><a
665 href="#lang-pseudo">The :lang()
666 pseudo-class</a></td>
667 <td class="origin">2</td></tr>
668 <tr>
669 <td class="pattern">E:enabled<br>E:disabled</td>
670 <td class="meaning">a user interface element E which is enabled or
671 disabled</td>
672 <td class="described"><a
673 href="#UIstates">The UI element states
674 pseudo-classes</a></td>
675 <td class="origin">3</td></tr>
676 <tr>
677 <td class="pattern">E:checked<!--<br>E:indeterminate--></td>
678 <td class="meaning">a user interface element E which is checked<!-- or in an
679 indeterminate state--> (for instance a radio-button or checkbox)</td>
680 <td class="described"><a
681 href="#UIstates">The UI element states
682 pseudo-classes</a></td>
683 <td class="origin">3</td></tr>
684 <tr>
685 <td class="pattern">E::first-line</td>
686 <td class="meaning">the first formatted line of an E element</td>
687 <td class="described"><a
688 href="#first-line">The ::first-line
689 pseudo-element</a></td>
690 <td class="origin">1</td></tr>
691 <tr>
692 <td class="pattern">E::first-letter</td>
693 <td class="meaning">the first formatted letter of an E element</td>
694 <td class="described"><a
695 href="#first-letter">The ::first-letter
696 pseudo-element</a></td>
697 <td class="origin">1</td></tr>
698 <tr>
699 <td class="pattern">E::selection</td>
700 <td class="meaning">the portion of an E element that is currently
701 selected/highlighted by the user</td>
702 <td class="described"><a
703 href="#UIfragments">The UI element
704 fragments pseudo-elements</a></td>
705 <td class="origin">3</td></tr>
706 <tr>
707 <td class="pattern">E::before</td>
708 <td class="meaning">generated content before an E element</td>
709 <td class="described"><a
710 href="#gen-content">The ::before
711 pseudo-element</a></td>
712 <td class="origin">2</td></tr>
713 <tr>
714 <td class="pattern">E::after</td>
715 <td class="meaning">generated content after an E element</td>
716 <td class="described"><a
717 href="#gen-content">The ::after
718 pseudo-element</a></td>
719 <td class="origin">2</td></tr>
720 <tr>
721 <td class="pattern">E.warning</td>
722 <td class="meaning">an E element whose class is
723 "warning" (the document language specifies how class is determined).</td>
724 <td class="described"><a
725 href="#class-html">Class
726 selectors</a></td>
727 <td class="origin">1</td></tr>
728 <tr>
729 <td class="pattern">E#myid</td>
730 <td class="meaning">an E element with ID equal to "myid".</td>
731 <td class="described"><a
732 href="#id-selectors">ID
733 selectors</a></td>
734 <td class="origin">1</td></tr>
735 <tr>
736 <td class="pattern">E:not(s)</td>
737 <td class="meaning">an E element that does not match simple selector s</td>
738 <td class="described"><a
739 href="#negation">Negation
740 pseudo-class</a></td>
741 <td class="origin">3</td></tr>
742 <tr>
743 <td class="pattern">E F</td>
744 <td class="meaning">an F element descendant of an E element</td>
745 <td class="described"><a
746 href="#descendant-combinators">Descendant
747 combinator</a></td>
748 <td class="origin">1</td></tr>
749 <tr>
750 <td class="pattern">E &gt; F</td>
751 <td class="meaning">an F element child of an E element</td>
752 <td class="described"><a
753 href="#child-combinators">Child
754 combinator</a></td>
755 <td class="origin">2</td></tr>
756 <tr>
757 <td class="pattern">E + F</td>
758 <td class="meaning">an F element immediately preceded by an E element</td>
759 <td class="described"><a
760 href="#adjacent-sibling-combinators">Adjacent sibling combinator</a></td>
761 <td class="origin">2</td></tr>
762 <tr>
763 <td class="pattern">E ~ F</td>
764 <td class="meaning">an F element preceded by an E element</td>
765 <td class="described"><a
766 href="#general-sibling-combinators">General sibling combinator</a></td>
767 <td class="origin">3</td></tr></tbody></table>
768
769 <p>The meaning of each selector is derived from the table above by
770 prepending "matches" to the contents of each cell in the "Meaning"
771 column.</p>
772
773 <h2><a name=casesens>3. Case sensitivity</a></h2>
774
775 <p>The case sensitivity of document language element names, attribute
776 names, and attribute values in selectors depends on the document
777 language. For example, in HTML, element names are case-insensitive,
778 but in XML, they are case-sensitive.</p>
779
780 <h2><a name=selector-syntax>4. Selector syntax</a></h2>
781
782 <p>A <dfn><a name=selector>selector</a></dfn> is a chain of one
783 or more <a href="#sequence">sequences of simple selectors</a>
784 separated by <a href="#combinators">combinators</a>.</p>
785
786 <p>A <dfn><a name=sequence>sequence of simple selectors</a></dfn>
787 is a chain of <a href="#simple-selectors-dfn">simple selectors</a>
788 that are not separated by a <a href="#combinators">combinator</a>. It
789 always begins with a <a href="#type-selectors">type selector</a> or a
790 <a href="#universal-selector">universal selector</a>. No other type
791 selector or universal selector is allowed in the sequence.</p>
792
793 <p>A <dfn><a name=simple-selectors-dfn></a><a
794 href="#simple-selectors">simple selector</a></dfn> is either a <a
795 href="#type-selectors">type selector</a>, <a
796 href="#universal-selector">universal selector</a>, <a
797 href="#attribute-selectors">attribute selector</a>, <a
798 href="#class-html">class selector</a>, <a
799 href="#id-selectors">ID selector</a>, <a
800 href="#content-selectors">content selector</a>, or <a
801 href="#pseudo-classes">pseudo-class</a>. One <a
802 href="#pseudo-elements">pseudo-element</a> may be appended to the last
803 sequence of simple selectors.</p>
804
805 <p><dfn>Combinators</dfn> are: white space, &quot;greater-than
806 sign&quot; (U+003E, <code>&gt;</code>), &quot;plus sign&quot; (U+002B,
807 <code>+</code>) and &quot;tilde&quot; (U+007E, <code>~</code>). White
808 space may appear between a combinator and the simple selectors around
809 it. <a name=whitespace></a>Only the characters "space" (U+0020), "tab"
810 (U+0009), "line feed" (U+000A), "carriage return" (U+000D), and "form
811 feed" (U+000C) can occur in white space. Other space-like characters,
812 such as "em-space" (U+2003) and "ideographic space" (U+3000), are
813 never part of white space.</p>
814
815 <p>The elements of a document tree that are represented by a selector
816 are the <dfn><a name=subject></a>subjects of the selector</dfn>. A
817 selector consisting of a single sequence of simple selectors
818 represents any element satisfying its requirements. Prepending another
819 sequence of simple selectors and a combinator to a sequence imposes
820 additional matching constraints, so the subjects of a selector are
821 always a subset of the elements represented by the last sequence of
822 simple selectors.</p>
823
824 <p>An empty selector, containing no sequence of simple selectors and
825 no pseudo-element, is an <a href="#Conformance">invalid
826 selector</a>.</p>
827
828 <h2><a name=grouping>5. Groups of selectors</a></h2>
829
830 <p>When several selectors share the same declarations, they may be
831 grouped into a comma-separated list. (A comma is U+002C.)</p>
832
833 <div class="example">
834 <p>CSS examples:</p>
835 <p>In this example, we condense three rules with identical
836 declarations into one. Thus,</p>
837 <pre>h1 { font-family: sans-serif }
838 h2 { font-family: sans-serif }
839 h3 { font-family: sans-serif }</pre>
840 <p>is equivalent to:</p>
841 <pre>h1, h2, h3 { font-family: sans-serif }</pre>
842 </div>
843
844 <p><strong>Warning</strong>: the equivalence is true in this example
845 because all the selectors are valid selectors. If just one of these
846 selectors were invalid, the entire group of selectors would be
847 invalid. This would invalidate the rule for all three heading
848 elements, whereas in the former case only one of the three individual
849 heading rules would be invalidated.</p>
850
851
852 <h2><a name=simple-selectors>6. Simple selectors</a></h2>
853
854 <h3><a name=type-selectors>6.1. Type selector</a></h3>
855
856 <p>A <dfn>type selector</dfn> is the name of a document language
857 element type. A type selector represents an instance of the element
858 type in the document tree.</p>
859
860 <div class="example">
861 <p>Example:</p>
862 <p>The following selector represents an <code>h1</code> element in the document tree:</p>
863 <pre>h1</pre>
864 </div>
865
866
867 <h4><a name=typenmsp>6.1.1. Type selectors and namespaces</a></h4>
868
869 <p>Type selectors allow an optional namespace (<a
870 href="#refsXMLNAMES">[XMLNAMES]</a>) component. A namespace prefix
871 that has been previously declared may be prepended to the element name
872 separated by the namespace separator &quot;vertical bar&quot;
873 (U+007C, <code>|</code>).</p>
874
875 <p>The namespace component may be left empty to indicate that the
876 selector is only to represent elements with no declared namespace.</p>
877
878 <p>An asterisk may be used for the namespace prefix, indicating that
879 the selector represents elements in any namespace (including elements
880 with no namespace).</p>
881
882 <p>Element type selectors that have no namespace component (no
883 namespace separator), represent elements without regard to the
884 element's namespace (equivalent to "<code>*|</code>") unless a default
885 namespace has been declared. If a default namespace has been declared,
886 the selector will represent only elements in the default
887 namespace.</p>
888
889 <p>A type selector containing a namespace prefix that has not been
890 previously declared is an <a href="#Conformance">invalid</a> selector.
891 The mechanism for declaring a namespace prefix is left up to the
892 language implementing Selectors. In CSS, such a mechanism is defined
893 in the General Syntax module.</p>
894
895 <p>In a namespace-aware client, element type selectors will only match
896 against the <a
897 href="http://www.w3.org/TR/REC-xml-names/#NT-LocalPart">local part</a>
898 of the element's <a
899 href="http://www.w3.org/TR/REC-xml-names/#ns-qualnames">qualified
900 name</a>. See <a href="#downlevel">below</a> for notes about matching
901 behaviors in down-level clients.</p>
902
903 <p>In summary:</p>
904
905 <dl>
906 <dt><code>ns|E</code></dt>
907 <dd>elements with name E in namespace ns</dd>
908 <dt><code>*|E</code></dt>
909 <dd>elements with name E in any namespace, including those without any
910 declared namespace</dd>
911 <dt><code>|E</code></dt>
912 <dd>elements with name E without any declared namespace</dd>
913 <dt><code>E</code></dt>
914 <dd>if no default namespace has been specified, this is equivalent to *|E.
915 Otherwise it is equivalent to ns|E where ns is the default namespace.</dd>
916 </dl>
917
918 <div class="example">
919 <p>CSS examples:</p>
920
921 <pre>@namespace foo url(http://www.example.com);
922 foo|h1 { color: blue }
923 foo|* { color: yellow }
924 |h1 { color: red }
925 *|h1 { color: green }
926 h1 { color: green }</pre>
927
928 <p>The first rule will match only <code>h1</code> elements in the
929 "http://www.example.com" namespace.</p>
930
931 <p>The second rule will match all elements in the
932 "http://www.example.com" namespace.</p>
933
934 <p>The third rule will match only <code>h1</code> elements without
935 any declared namespace.</p>
936
937 <p>The fourth rule will match <code>h1</code> elements in any
938 namespace (including those without any declared namespace).</p>
939
940 <p>The last rule is equivalent to the fourth rule because no default
941 namespace has been defined.</p>
942
943 </div>
944
945 <h3><a name=universal-selector>6.2. Universal selector</a> </h3>
946
947 <p>The <dfn>universal selector</dfn>, written &quot;asterisk&quot;
948 (<code>*</code>), represents the qualified name of any element
949 type. It represents any single element in the document tree in any
950 namespace (including those without any declared namespace) if no
951 default namespace has been specified. If a default namespace has been
952 specified, see <a href="#univnmsp">Universal selector and
953 Namespaces</a> below.</p>
954
955 <p>If the universal selector is not the only component of a sequence
956 of simple selectors, the <code>*</code> may be omitted.</p>
957
958 <div class="example">
959 <p>Examples:</p>
960 <ul>
961 <li><code>*[hreflang|=en]</code> and <code>[hreflang|=en]</code> are equivalen t,</li>
962 <li><code>*.warning</code> and <code>.warning</code> are equivalent,</li>
963 <li><code>*#myid</code> and <code>#myid</code> are equivalent.</li>
964 </ul>
965 </div>
966
967 <p class="note"><strong>Note:</strong> it is recommended that the
968 <code>*</code>, representing the universal selector, not be
969 omitted.</p>
970
971 <h4><a name=univnmsp>6.2.1. Universal selector and namespaces</a></h4>
972
973 <p>The universal selector allows an optional namespace component. It
974 is used as follows:</p>
975
976 <dl>
977 <dt><code>ns|*</code></dt>
978 <dd>all elements in namespace ns</dd>
979 <dt><code>*|*</code></dt>
980 <dd>all elements</dd>
981 <dt><code>|*</code></dt>
982 <dd>all elements without any declared namespace</dd>
983 <dt><code>*</code></dt>
984 <dd>if no default namespace has been specified, this is equivalent to *|*.
985 Otherwise it is equivalent to ns|* where ns is the default namespace.</dd>
986 </dl>
987
988 <p>A universal selector containing a namespace prefix that has not
989 been previously declared is an <a href="#Conformance">invalid</a>
990 selector. The mechanism for declaring a namespace prefix is left up
991 to the language implementing Selectors. In CSS, such a mechanism is
992 defined in the General Syntax module.</p>
993
994
995 <h3><a name=attribute-selectors>6.3. Attribute selectors</a></h3>
996
997 <p>Selectors allow the representation of an element's attributes. When
998 a selector is used as an expression to match against an element,
999 attribute selectors must be considered to match an element if that
1000 element has an attribute that matches the attribute represented by the
1001 attribute selector.</p>
1002
1003 <h4><a name=attribute-representation>6.3.1. Attribute presence and values
1004 selectors</a></h4>
1005
1006 <p>CSS2 introduced four attribute selectors:</p>
1007
1008 <dl>
1009 <dt><code>[att]</code>
1010 <dd>Represents an element with the <code>att</code> attribute, whatever the va lue of
1011 the attribute.</dd>
1012 <dt><code>[att=val]</code></dt>
1013 <dd>Represents an element with the <code>att</code> attribute whose value is e xactly
1014 "val".</dd>
1015 <dt><code>[att~=val]</code></dt>
1016 <dd>Represents an element with the <code>att</code> attribute whose value is a <a
1017 href="#whitespace">whitespace</a>-separated list of words, one of
1018 which is exactly "val". If "val" contains whitespace, it will never
1019 represent anything (since the words are <em>separated</em> by
1020 spaces).</dd>
1021 <dt><code>[att|=val]</code>
1022 <dd>Represents an element with the <code>att</code> attribute, its value eithe r
1023 being exactly "val" or beginning with "val" immediately followed by
1024 "-" (U+002D). This is primarily intended to allow language subcode
1025 matches (e.g., the <code>hreflang</code> attribute on the
1026 <code>link</code> element in HTML) as described in RFC 3066 (<a
1027 href="#refsRFC3066">[RFC3066]</a>). For <code>lang</code> (or
1028 <code>xml:lang</code>) language subcode matching, please see <a
1029 href="#lang-pseudo">the <code>:lang</code> pseudo-class</a>.</dd>
1030 </dl>
1031
1032 <p>Attribute values must be identifiers or strings. The
1033 case-sensitivity of attribute names and values in selectors depends on
1034 the document language.</p>
1035
1036 <div class="example">
1037
1038 <p>Examples:</p>
1039
1040 <p>The following attribute selector represents an <code>h1</code>
1041 element that carries the <code>title</code> attribute, whatever its
1042 value:</p>
1043
1044 <pre>h1[title]</pre>
1045
1046 <p>In the following example, the selector represents a
1047 <code>span</code> element whose <code>class</code> attribute has
1048 exactly the value "example":</p>
1049
1050 <pre>span[class="example"]</pre>
1051
1052 <p>Multiple attribute selectors can be used to represent several
1053 attributes of an element, or several conditions on the same
1054 attribute. Here, the selector represents a <code>span</code> element
1055 whose <code>hello</code> attribute has exactly the value "Cleveland"
1056 and whose <code>goodbye</code> attribute has exactly the value
1057 "Columbus":</p>
1058
1059 <pre>span[hello="Cleveland"][goodbye="Columbus"]</pre>
1060
1061 <p>The following selectors illustrate the differences between "="
1062 and "~=". The first selector will represent, for example, the value
1063 "copyright copyleft copyeditor" on a <code>rel</code> attribute. The
1064 second selector will only represent an <code>a</code> element with
1065 an <code>href</code> attribute having the exact value
1066 "http://www.w3.org/".</p>
1067
1068 <pre>a[rel~="copyright"]
1069 a[href="http://www.w3.org/"]</pre>
1070
1071 <p>The following selector represents a <code>link</code> element
1072 whose <code>hreflang</code> attribute is exactly "fr".</p>
1073
1074 <pre>link[hreflang=fr]</pre>
1075
1076 <p>The following selector represents a <code>link</code> element for
1077 which the values of the <code>hreflang</code> attribute begins with
1078 "en", including "en", "en-US", and "en-cockney":</p>
1079
1080 <pre>link[hreflang|="en"]</pre>
1081
1082 <p>Similarly, the following selectors represents a
1083 <code>DIALOGUE</code> element whenever it has one of two different
1084 values for an attribute <code>character</code>:</p>
1085
1086 <pre>DIALOGUE[character=romeo]
1087 DIALOGUE[character=juliet]</pre>
1088
1089 </div>
1090
1091 <h4><a name=attribute-substrings></a>6.3.2. Substring matching attribute
1092 selectors</h4>
1093
1094 <p>Three additional attribute selectors are provided for matching
1095 substrings in the value of an attribute:</p>
1096
1097 <dl>
1098 <dt><code>[att^=val]</code></dt>
1099 <dd>Represents an element with the <code>att</code> attribute whose value begi ns
1100 with the prefix "val".</dd>
1101 <dt><code>[att$=val]</code>
1102 <dd>Represents an element with the <code>att</code> attribute whose value ends with
1103 the suffix "val".</dd>
1104 <dt><code>[att*=val]</code>
1105 <dd>Represents an element with the <code>att</code> attribute whose value cont ains
1106 at least one instance of the substring "val".</dd>
1107 </dl>
1108
1109 <p>Attribute values must be identifiers or strings. The
1110 case-sensitivity of attribute names in selectors depends on the
1111 document language.</p>
1112
1113 <div class="example">
1114 <p>Examples:</p>
1115 <p>The following selector represents an HTML <code>object</code>, referencing a n
1116 image:</p>
1117 <pre>object[type^="image/"]</pre>
1118 <p>The following selector represents an HTML anchor <code>a</code> with an
1119 <code>href</code> attribute whose value ends with ".html".</p>
1120 <pre>a[href$=".html"]</pre>
1121 <p>The following selector represents an HTML paragraph with a <code>title</code >
1122 attribute whose value contains the substring "hello"</p>
1123 <pre>p[title*="hello"]</pre>
1124 </div>
1125
1126 <h4><a name=attrnmsp>6.3.3. Attribute selectors and namespaces</a></h4>
1127
1128 <p>Attribute selectors allow an optional namespace component to the
1129 attribute name. A namespace prefix that has been previously declared
1130 may be prepended to the attribute name separated by the namespace
1131 separator &quot;vertical bar&quot; (<code>|</code>). In keeping with
1132 the Namespaces in the XML recommendation, default namespaces do not
1133 apply to attributes, therefore attribute selectors without a namespace
1134 component apply only to attributes that have no declared namespace
1135 (equivalent to "<code>|attr</code>"). An asterisk may be used for the
1136 namespace prefix indicating that the selector is to match all
1137 attribute names without regard to the attribute's namespace.
1138
1139 <p>An attribute selector with an attribute name containing a namespace
1140 prefix that has not been previously declared is an <a
1141 href="#Conformance">invalid</a> selector. The mechanism for declaring
1142 a namespace prefix is left up to the language implementing Selectors.
1143 In CSS, such a mechanism is defined in the General Syntax module.
1144
1145 <div class="example">
1146 <p>CSS examples:</p>
1147 <pre>@namespace foo "http://www.example.com";
1148 [foo|att=val] { color: blue }
1149 [*|att] { color: yellow }
1150 [|att] { color: green }
1151 [att] { color: green }</pre>
1152
1153 <p>The first rule will match only elements with the attribute
1154 <code>att</code> in the "http://www.example.com" namespace with the
1155 value "val".</p>
1156
1157 <p>The second rule will match only elements with the attribute
1158 <code>att</code> regardless of the namespace of the attribute
1159 (including no declared namespace).</p>
1160
1161 <p>The last two rules are equivalent and will match only elements
1162 with the attribute <code>att</code> where the attribute is not
1163 declared to be in a namespace.</p>
1164
1165 </div>
1166
1167 <h4><a name=def-values>6.3.4. Default attribute values in DTDs</a></h4>
1168
1169 <p>Attribute selectors represent explicitly set attribute values in
1170 the document tree. Default attribute values may be defined in a DTD or
1171 elsewhere, but cannot always be selected by attribute
1172 selectors. Selectors should be designed so that they work even if the
1173 default values are not included in the document tree.</p>
1174
1175 <p>More precisely, a UA is <em>not</em> required to read an "external
1176 subset" of the DTD but <em>is</em> required to look for default
1177 attribute values in the document's "internal subset." (See <a
1178 href="#refsXML10">[XML10]</a> for definitions of these subsets.)</p>
1179
1180 <p>A UA that recognizes an XML namespace <a
1181 href="#refsXMLNAMES">[XMLNAMES]</a> is not required to use its
1182 knowledge of that namespace to treat default attribute values as if
1183 they were present in the document. (For example, an XHTML UA is not
1184 required to use its built-in knowledge of the XHTML DTD.)</p>
1185
1186 <p class="note"><strong>Note:</strong> Typically, implementations
1187 choose to ignore external subsets.</p>
1188
1189 <div class="example">
1190 <p>Example:</p>
1191
1192 <p>Consider an element EXAMPLE with an attribute "notation" that has a
1193 default value of "decimal". The DTD fragment might be</p>
1194
1195 <pre class="dtd-example">&lt;!ATTLIST EXAMPLE notation (decimal,octal) "decimal" ></pre>
1196
1197 <p>If the style sheet contains the rules</p>
1198
1199 <pre>EXAMPLE[notation=decimal] { /*... default property settings ...*/ }
1200 EXAMPLE[notation=octal] { /*... other settings...*/ }</pre>
1201
1202 <p>the first rule will not match elements whose "notation" attribute
1203 is set by default, i.e. not set explicitly. To catch all cases, the
1204 attribute selector for the default value must be dropped:</p>
1205
1206 <pre>EXAMPLE { /*... default property settings ...*/ }
1207 EXAMPLE[notation=octal] { /*... other settings...*/ }</pre>
1208
1209 <p>Here, because the selector <code>EXAMPLE[notation=octal]</code> is
1210 more specific than the tag
1211 selector alone, the style declarations in the second rule will override
1212 those in the first for elements that have a "notation" attribute value
1213 of "octal". Care has to be taken that all property declarations that
1214 are to apply only to the default case are overridden in the non-default
1215 cases' style rules.</p>
1216
1217 </div>
1218
1219 <h3><a name=class-html>6.4. Class selectors</a></h3>
1220
1221 <p>Working with HTML, authors may use the period (U+002E,
1222 <code>.</code>) notation as an alternative to the <code>~=</code>
1223 notation when representing the <code>class</code> attribute. Thus, for
1224 HTML, <code>div.value</code> and <code>div[class~=value]</code> have
1225 the same meaning. The attribute value must immediately follow the
1226 &quot;period&quot; (<code>.</code>).</p>
1227
1228 <p>UAs may apply selectors using the period (.) notation in XML
1229 documents if the UA has namespace-specific knowledge that allows it to
1230 determine which attribute is the &quot;class&quot; attribute for the
1231 respective namespace. One such example of namespace-specific knowledge
1232 is the prose in the specification for a particular namespace (e.g. SVG
1233 1.0 <a href="#refsSVG">[SVG]</a> describes the <a
1234 href="http://www.w3.org/TR/2001/PR-SVG-20010719/styling.html#ClassAttribute">SVG
1235 &quot;class&quot; attribute</a> and how a UA should interpret it, and
1236 similarly MathML 1.01 <a href="#refsMATH">[MATH]</a> describes the <a
1237 href="http://www.w3.org/1999/07/REC-MathML-19990707/chapter2.html#sec2.3.4">Math ML
1238 &quot;class&quot; attribute</a>.)</p>
1239
1240 <div class="example">
1241 <p>CSS examples:</p>
1242
1243 <p>We can assign style information to all elements with
1244 <code>class~="pastoral"</code> as follows:</p>
1245
1246 <pre>*.pastoral { color: green } /* all elements with class~=pastoral */</pre >
1247
1248 <p>or just</p>
1249
1250 <pre>.pastoral { color: green } /* all elements with class~=pastoral */</pre>
1251
1252 <p>The following assigns style only to H1 elements with
1253 <code>class~="pastoral"</code>:</p>
1254
1255 <pre>H1.pastoral { color: green } /* H1 elements with class~=pastoral */</pre >
1256
1257 <p>Given these rules, the first H1 instance below would not have
1258 green text, while the second would:</p>
1259
1260 <pre>&lt;H1&gt;Not green&lt;/H1&gt;
1261 &lt;H1 class="pastoral"&gt;Very green&lt;/H1&gt;</pre>
1262
1263 </div>
1264
1265 <p>To represent a subset of "class" values, each value must be preceded
1266 by a ".", in any order.</P>
1267
1268 <div class="example">
1269
1270 <p>CSS example:</p>
1271
1272 <p>The following rule matches any P element whose "class" attribute
1273 has been assigned a list of <a
1274 href="#whitespace">whitespace</a>-separated values that includes
1275 "pastoral" and "marine":</p>
1276
1277 <pre>p.pastoral.marine { color: green }</pre>
1278
1279 <p>This rule matches when <code>class="pastoral blue aqua
1280 marine"</code> but does not match for <code>class="pastoral
1281 blue"</code>.</p>
1282
1283 </div>
1284
1285 <p class="note"><strong>Note:</strong> Because CSS gives considerable
1286 power to the "class" attribute, authors could conceivably design their
1287 own "document language" based on elements with almost no associated
1288 presentation (such as DIV and SPAN in HTML) and assigning style
1289 information through the "class" attribute. Authors should avoid this
1290 practice since the structural elements of a document language often
1291 have recognized and accepted meanings and author-defined classes may
1292 not.</p>
1293
1294 <p class="note"><strong>Note:</strong> If an element has multiple
1295 class attributes, their values must be concatenated with spaces
1296 between the values before searching for the class. As of this time the
1297 working group is not aware of any manner in which this situation can
1298 be reached, however, so this behavior is explicitly non-normative in
1299 this specification.</p>
1300
1301 <h3><a name=id-selectors>6.5. ID selectors</a></h3>
1302
1303 <p>Document languages may contain attributes that are declared to be
1304 of type ID. What makes attributes of type ID special is that no two
1305 such attributes can have the same value in a document, regardless of
1306 the type of the elements that carry them; whatever the document
1307 language, an ID typed attribute can be used to uniquely identify its
1308 element. In HTML all ID attributes are named "id"; XML applications
1309 may name ID attributes differently, but the same restriction
1310 applies.</p>
1311
1312 <p>An ID-typed attribute of a document language allows authors to
1313 assign an identifier to one element instance in the document tree. W3C
1314 ID selectors represent an element instance based on its identifier. An
1315 ID selector contains a &quot;number sign&quot; (U+0023,
1316 <code>#</code>) immediately followed by the ID value, which must be an
1317 identifier.</p>
1318
1319 <p>Selectors does not specify how a UA knows the ID-typed attribute of
1320 an element. The UA may, e.g., read a document's DTD, have the
1321 information hard-coded or ask the user.
1322
1323 <div class="example">
1324 <p>Examples:</p>
1325 <p>The following ID selector represents an <code>h1</code> element
1326 whose ID-typed attribute has the value "chapter1":</p>
1327 <pre>h1#chapter1</pre>
1328 <p>The following ID selector represents any element whose ID-typed
1329 attribute has the value "chapter1":</p>
1330 <pre>#chapter1</pre>
1331 <p>The following selector represents any element whose ID-typed
1332 attribute has the value "z98y".</p>
1333 <pre>*#z98y</pre>
1334 </div>
1335
1336 <p class="note"><strong>Note.</strong> In XML 1.0 <a
1337 href="#refsXML10">[XML10]</a>, the information about which attribute
1338 contains an element's IDs is contained in a DTD or a schema. When
1339 parsing XML, UAs do not always read the DTD, and thus may not know
1340 what the ID of an element is (though a UA may have namespace-specific
1341 knowledge that allows it to determine which attribute is the ID
1342 attribute for that namespace). If a style sheet designer knows or
1343 suspects that a UA may not know what the ID of an element is, he
1344 should use normal attribute selectors instead:
1345 <code>[name=p371]</code> instead of <code>#p371</code>. Elements in
1346 XML 1.0 documents without a DTD do not have IDs at all.</p>
1347
1348 <p>If an element has multiple ID attributes, all of them must be
1349 treated as IDs for that element for the purposes of the ID
1350 selector. Such a situation could be reached using mixtures of xml:id,
1351 DOM3 Core, XML DTDs, and namespace-specific knowledge.</p>
1352
1353 <h3><a name=pseudo-classes>6.6. Pseudo-classes</a></h3>
1354
1355 <p>The pseudo-class concept is introduced to permit selection based on
1356 information that lies outside of the document tree or that cannot be
1357 expressed using the other simple selectors.</p>
1358
1359 <p>A pseudo-class always consists of a &quot;colon&quot;
1360 (<code>:</code>) followed by the name of the pseudo-class and
1361 optionally by a value between parentheses.</p>
1362
1363 <p>Pseudo-classes are allowed in all sequences of simple selectors
1364 contained in a selector. Pseudo-classes are allowed anywhere in
1365 sequences of simple selectors, after the leading type selector or
1366 universal selector (possibly omitted). Pseudo-class names are
1367 case-insensitive. Some pseudo-classes are mutually exclusive, while
1368 others can be applied simultaneously to the same
1369 element. Pseudo-classes may be dynamic, in the sense that an element
1370 may acquire or lose a pseudo-class while a user interacts with the
1371 document.</p>
1372
1373
1374 <h4><a name=dynamic-pseudos>6.6.1. Dynamic pseudo-classes</a></h4>
1375
1376 <p>Dynamic pseudo-classes classify elements on characteristics other
1377 than their name, attributes, or content, in principle characteristics
1378 that cannot be deduced from the document tree.</p>
1379
1380 <p>Dynamic pseudo-classes do not appear in the document source or
1381 document tree.</p>
1382
1383
1384 <h5>The <a name=link>link pseudo-classes: :link and :visited</a></h5>
1385
1386 <p>User agents commonly display unvisited links differently from
1387 previously visited ones. Selectors
1388 provides the pseudo-classes <code>:link</code> and
1389 <code>:visited</code> to distinguish them:</p>
1390
1391 <ul>
1392 <li>The <code>:link</code> pseudo-class applies to links that have
1393 not yet been visited.</li>
1394 <li>The <code>:visited</code> pseudo-class applies once the link has
1395 been visited by the user. </li>
1396 </ul>
1397
1398 <p>After some amount of time, user agents may choose to return a
1399 visited link to the (unvisited) ':link' state.</p>
1400
1401 <p>The two states are mutually exclusive.</p>
1402
1403 <div class="example">
1404
1405 <p>Example:</p>
1406
1407 <p>The following selector represents links carrying class
1408 <code>external</code> and already visited:</p>
1409
1410 <pre>a.external:visited</pre>
1411
1412 </div>
1413
1414 <p class="note"><strong>Note:</strong> It is possible for style sheet
1415 authors to abuse the :link and :visited pseudo-classes to determine
1416 which sites a user has visited without the user's consent.
1417
1418 <p>UAs may therefore treat all links as unvisited links, or implement
1419 other measures to preserve the user's privacy while rendering visited
1420 and unvisited links differently.</p>
1421
1422 <h5>The <a name=useraction-pseudos>user action pseudo-classes
1423 :hover, :active, and :focus</a></h5>
1424
1425 <p>Interactive user agents sometimes change the rendering in response
1426 to user actions. Selectors provides
1427 three pseudo-classes for the selection of an element the user is
1428 acting on.</p>
1429
1430 <ul>
1431
1432 <li>The <code>:hover</code> pseudo-class applies while the user
1433 designates an element with a pointing device, but does not activate
1434 it. For example, a visual user agent could apply this pseudo-class
1435 when the cursor (mouse pointer) hovers over a box generated by the
1436 element. User agents not that do not support <a
1437 href="http://www.w3.org/TR/REC-CSS2/media.html#interactive-media-group">intera ctive
1438 media</a> do not have to support this pseudo-class. Some conforming
1439 user agents that support <a
1440 href="http://www.w3.org/TR/REC-CSS2/media.html#interactive-media-group">intera ctive
1441 media</a> may not be able to support this pseudo-class (e.g., a pen
1442 device that does not detect hovering).</li>
1443
1444 <li>The <code>:active</code> pseudo-class applies while an element
1445 is being activated by the user. For example, between the times the
1446 user presses the mouse button and releases it.</li>
1447
1448 <li>The <code>:focus</code> pseudo-class applies while an element
1449 has the focus (accepts keyboard or mouse events, or other forms of
1450 input). </li>
1451
1452 </ul>
1453
1454 <p>There may be document language or implementation specific limits on
1455 which elements can become <code>:active</code> or acquire
1456 <code>:focus</code>.</p>
1457
1458 <p>These pseudo-classes are not mutually exclusive. An element may
1459 match several pseudo-classes at the same time.</p>
1460
1461 <p>Selectors doesn't define if the parent of an element that is
1462 ':active' or ':hover' is also in that state.</p>
1463
1464 <div class="example">
1465 <p>Examples:</p>
1466 <pre>a:link /* unvisited links */
1467 a:visited /* visited links */
1468 a:hover /* user hovers */
1469 a:active /* active links */</pre>
1470 <p>An example of combining dynamic pseudo-classes:</p>
1471 <pre>a:focus
1472 a:focus:hover</pre>
1473 <p>The last selector matches <code>a</code> elements that are in
1474 the pseudo-class :focus and in the pseudo-class :hover.</p>
1475 </div>
1476
1477 <p class="note"><strong>Note:</strong> An element can be both ':visited'
1478 and ':active' (or ':link' and ':active').</p>
1479
1480 <h4><a name=target-pseudo>6.6.2. The target pseudo-class :target</a></h4>
1481
1482 <p>Some URIs refer to a location within a resource. This kind of URI
1483 ends with a &quot;number sign&quot; (#) followed by an anchor
1484 identifier (called the fragment identifier).</p>
1485
1486 <p>URIs with fragment identifiers link to a certain element within the
1487 document, known as the target element. For instance, here is a URI
1488 pointing to an anchor named <code>section_2</code> in an HTML
1489 document:</p>
1490
1491 <pre>http://example.com/html/top.html#section_2</pre>
1492
1493 <p>A target element can be represented by the <code>:target</code>
1494 pseudo-class. If the document's URI has no fragment identifier, then
1495 the document has no target element.</p>
1496
1497 <div class="example">
1498 <p>Example:</p>
1499 <pre>p.note:target</pre>
1500 <p>This selector represents a <code>p</code> element of class
1501 <code>note</code> that is the target element of the referring
1502 URI.</p>
1503 </div>
1504
1505 <div class="example">
1506 <p>CSS example:</p>
1507 <p>Here, the <code>:target</code> pseudo-class is used to make the
1508 target element red and place an image before it, if there is one:</p>
1509 <pre>*:target { color : red }
1510 *:target::before { content : url(target.png) }</pre>
1511 </div>
1512
1513 <h4><a name=lang-pseudo>6.6.3. The language pseudo-class :lang</a></h4>
1514
1515 <p>If the document language specifies how the human language of an
1516 element is determined, it is possible to write selectors that
1517 represent an element based on its language. For example, in HTML <a
1518 href="#refsHTML4">[HTML4]</a>, the language is determined by a
1519 combination of the <code>lang</code> attribute, the <code>meta</code>
1520 element, and possibly by information from the protocol (such as HTTP
1521 headers). XML uses an attribute called <code>xml:lang</code>, and
1522 there may be other document language-specific methods for determining
1523 the language.</p>
1524
1525 <p>The pseudo-class <code>:lang(C)</code> represents an element that
1526 is in language C. Whether an element is represented by a
1527 <code>:lang()</code> selector is based solely on the identifier C
1528 being either equal to, or a hyphen-separated substring of, the
1529 element's language value, in the same way as if performed by the <a
1530 href="#attribute-representation">'|='</a> operator in attribute
1531 selectors. The identifier C does not have to be a valid language
1532 name.</p>
1533
1534 <p>C must not be empty. (If it is, the selector is invalid.)</p>
1535
1536 <p class="note"><strong>Note:</strong> It is recommended that
1537 documents and protocols indicate language using codes from RFC 3066 <a
1538 href="#refsRFC3066">[RFC3066]</a> or its successor, and by means of
1539 "xml:lang" attributes in the case of XML-based documents <a
1540 href="#refsXML10">[XML10]</a>. See <a
1541 href="http://www.w3.org/International/questions/qa-lang-2or3.html">
1542 "FAQ: Two-letter or three-letter language codes."</a></p>
1543
1544 <div class="example">
1545 <p>Examples:</p>
1546 <p>The two following selectors represent an HTML document that is in
1547 Belgian, French, or German. The two next selectors represent
1548 <code>q</code> quotations in an arbitrary element in Belgian, French,
1549 or German.</p>
1550 <pre>html:lang(fr-be)
1551 html:lang(de)
1552 :lang(fr-be) &gt; q
1553 :lang(de) &gt; q</pre>
1554 </div>
1555
1556 <h4><a name=UIstates>6.6.4. The UI element states pseudo-classes</a></h4>
1557
1558 <h5><a name=enableddisabled>The :enabled and :disabled pseudo-classes</a></h5>
1559
1560 <p>The <code>:enabled</code> pseudo-class allows authors to customize
1561 the look of user interface elements that are enabled &mdash; which the
1562 user can select or activate in some fashion (e.g. clicking on a button
1563 with a mouse). There is a need for such a pseudo-class because there
1564 is no way to programmatically specify the default appearance of say,
1565 an enabled <code>input</code> element without also specifying what it
1566 would look like when it was disabled.</p>
1567
1568 <p>Similar to <code>:enabled</code>, <code>:disabled</code> allows the
1569 author to specify precisely how a disabled or inactive user interface
1570 element should look.</p>
1571
1572 <p>Most elements will be neither enabled nor disabled. An element is
1573 enabled if the user can either activate it or transfer the focus to
1574 it. An element is disabled if it could be enabled, but the user cannot
1575 presently activate it or transfer focus to it.</p>
1576
1577
1578 <h5><a name=checked>The :checked pseudo-class</a></h5>
1579
1580 <p>Radio and checkbox elements can be toggled by the user. Some menu
1581 items are "checked" when the user selects them. When such elements are
1582 toggled "on" the <code>:checked</code> pseudo-class applies. The
1583 <code>:checked</code> pseudo-class initially applies to such elements
1584 that have the HTML4 <code>selected</code> and <code>checked</code>
1585 attributes as described in <a
1586 href="http://www.w3.org/TR/REC-html40/interact/forms.html#h-17.2.1">Section
1587 17.2.1 of HTML4</a>, but of course the user can toggle "off" such
1588 elements in which case the <code>:checked</code> pseudo-class would no
1589 longer apply. While the <code>:checked</code> pseudo-class is dynamic
1590 in nature, and is altered by user action, since it can also be based
1591 on the presence of the semantic HTML4 <code>selected</code> and
1592 <code>checked</code> attributes, it applies to all media.
1593
1594
1595 <h5><a name=indeterminate>The :indeterminate pseudo-class</a></h5>
1596
1597 <div class="note">
1598
1599 <p>Radio and checkbox elements can be toggled by the user, but are
1600 sometimes in an indeterminate state, neither checked nor unchecked.
1601 This can be due to an element attribute, or DOM manipulation.</p>
1602
1603 <p>A future version of this specification may introduce an
1604 <code>:indeterminate</code> pseudo-class that applies to such elements.
1605 <!--While the <code>:indeterminate</code> pseudo-class is dynamic in
1606 nature, and is altered by user action, since it can also be based on
1607 the presence of an element attribute, it applies to all media.</p>
1608
1609 <p>Components of a radio-group initialized with no pre-selected choice
1610 are an example of :indeterminate state.--></p>
1611
1612 </div>
1613
1614
1615 <h4><a name=structural-pseudos>6.6.5. Structural pseudo-classes</a></h4>
1616
1617 <p>Selectors introduces the concept of <dfn>structural
1618 pseudo-classes</dfn> to permit selection based on extra information that lies in
1619 the document tree but cannot be represented by other simple selectors or
1620 combinators.
1621
1622 <p>Note that standalone pieces of PCDATA (text nodes in the DOM) are
1623 not counted when calculating the position of an element in the list of
1624 children of its parent. When calculating the position of an element in
1625 the list of children of its parent, the index numbering starts at 1.
1626
1627
1628 <h5><a name=root-pseudo>:root pseudo-class</a></h5>
1629
1630 <p>The <code>:root</code> pseudo-class represents an element that is
1631 the root of the document. In HTML 4, this is always the
1632 <code>HTML</code> element.
1633
1634
1635 <h5><a name=nth-child-pseudo>:nth-child() pseudo-class</a></h5>
1636
1637 <p>The
1638 <code>:nth-child(<var>a</var><code>n</code>+<var>b</var>)</code>
1639 pseudo-class notation represents an element that has
1640 <var>a</var><code>n</code>+<var>b</var>-1 siblings
1641 <strong>before</strong> it in the document tree, for a given positive
1642 integer or zero value of <code>n</code>, and has a parent element. In
1643 other words, this matches the <var>b</var>th child of an element after
1644 all the children have been split into groups of <var>a</var> elements
1645 each. For example, this allows the selectors to address every other
1646 row in a table, and could be used to alternate the color
1647 of paragraph text in a cycle of four. The <var>a</var> and
1648 <var>b</var> values must be zero, negative integers or positive
1649 integers. The index of the first child of an element is 1.
1650
1651 <p>In addition to this, <code>:nth-child()</code> can take
1652 '<code>odd</code>' and '<code>even</code>' as arguments instead.
1653 '<code>odd</code>' has the same signification as <code>2n+1</code>,
1654 and '<code>even</code>' has the same signification as <code>2n</code>.
1655
1656
1657 <div class="example">
1658 <p>Examples:</p>
1659 <pre>tr:nth-child(2n+1) /* represents every odd row of an HTML table */
1660 tr:nth-child(odd) /* same */
1661 tr:nth-child(2n) /* represents every even row of an HTML table */
1662 tr:nth-child(even) /* same */
1663
1664 /* Alternate paragraph colours in CSS */
1665 p:nth-child(4n+1) { color: navy; }
1666 p:nth-child(4n+2) { color: green; }
1667 p:nth-child(4n+3) { color: maroon; }
1668 p:nth-child(4n+4) { color: purple; }</pre>
1669 </div>
1670
1671 <p>When <var>a</var>=0, no repeating is used, so for example
1672 <code>:nth-child(0n+5)</code> matches only the fifth child. When
1673 <var>a</var>=0, the <var>a</var><code>n</code> part need not be
1674 included, so the syntax simplifies to
1675 <code>:nth-child(<var>b</var>)</code> and the last example simplifies
1676 to <code>:nth-child(5)</code>.
1677
1678 <div class="example">
1679 <p>Examples:</p>
1680 <pre>foo:nth-child(0n+1) /* represents an element foo, first child of its pare nt element */
1681 foo:nth-child(1) /* same */</pre>
1682 </div>
1683
1684 <p>When <var>a</var>=1, the number may be omitted from the rule.
1685
1686 <div class="example">
1687 <p>Examples:</p>
1688 <p>The following selectors are therefore equivalent:</p>
1689 <pre>bar:nth-child(1n+0) /* represents all bar elements, specificity (0,1,1) * /
1690 bar:nth-child(n+0) /* same */
1691 bar:nth-child(n) /* same */
1692 bar /* same but lower specificity (0,0,1) */</pre>
1693 </div>
1694
1695 <p>If <var>b</var>=0, then every <var>a</var>th element is picked. In
1696 such a case, the <var>b</var> part may be omitted.
1697
1698 <div class="example">
1699 <p>Examples:</p>
1700 <pre>tr:nth-child(2n+0) /* represents every even row of an HTML table */
1701 tr:nth-child(2n) /* same */</pre>
1702 </div>
1703
1704 <p>If both <var>a</var> and <var>b</var> are equal to zero, the
1705 pseudo-class represents no element in the document tree.</p>
1706
1707 <p>The value <var>a</var> can be negative, but only the positive
1708 values of <var>a</var><code>n</code>+<var>b</var>, for
1709 <code>n</code>&ge;0, may represent an element in the document
1710 tree.</p>
1711
1712 <div class="example">
1713 <p>Example:</p>
1714 <pre>html|tr:nth-child(-n+6) /* represents the 6 first rows of XHTML tables */< /pre>
1715 </div>
1716
1717 <p>When the value <var>b</var> is negative, the "+" character in the
1718 expression must be removed (it is effectively replaced by the "-"
1719 character indicating the negative value of <var>b</var>).</p>
1720
1721 <div class="example">
1722 <p>Examples:</p>
1723 <pre>:nth-child(10n-1) /* represents the 9th, 19th, 29th, etc, element */
1724 :nth-child(10n+9) /* Same */
1725 :nth-child(10n+-1) /* Syntactically invalid, and would be ignored */</pre>
1726 </div>
1727
1728
1729 <h5><a name=nth-last-child-pseudo>:nth-last-child() pseudo-class</a></h5>
1730
1731 <p>The <code>:nth-last-child(<var>a</var>n+<var>b</var>)</code>
1732 pseudo-class notation represents an element that has
1733 <var>a</var><code>n</code>+<var>b</var>-1 siblings
1734 <strong>after</strong> it in the document tree, for a given positive
1735 integer or zero value of <code>n</code>, and has a parent element. See
1736 <code>:nth-child()</code> pseudo-class for the syntax of its argument.
1737 It also accepts the '<code>even</code>' and '<code>odd</code>' values
1738 as arguments.
1739
1740
1741 <div class="example">
1742 <p>Examples:</p>
1743 <pre>tr:nth-last-child(-n+2) /* represents the two last rows of an HTML table */
1744
1745 foo:nth-last-child(odd) /* represents all odd foo elements in their parent el ement,
1746 counting from the last one */</pre>
1747 </div>
1748
1749
1750 <h5><a name=nth-of-type-pseudo>:nth-of-type() pseudo-class</a></h5>
1751
1752 <p>The <code>:nth-of-type(<var>a</var>n+<var>b</var>)</code>
1753 pseudo-class notation represents an element that has
1754 <var>a</var><code>n</code>+<var>b</var>-1 siblings with the same
1755 element name <strong>before</strong> it in the document tree, for a
1756 given zero or positive integer value of <code>n</code>, and has a
1757 parent element. In other words, this matches the <var>b</var>th child
1758 of that type after all the children of that type have been split into
1759 groups of a elements each. See <code>:nth-child()</code> pseudo-class
1760 for the syntax of its argument. It also accepts the
1761 '<code>even</code>' and '<code>odd</code>' values.
1762
1763
1764 <div class="example">
1765 <p>CSS example:</p>
1766 <p>This allows an author to alternate the position of floated images:</p>
1767 <pre>img:nth-of-type(2n+1) { float: right; }
1768 img:nth-of-type(2n) { float: left; }</pre>
1769 </div>
1770
1771
1772 <h5><a name=nth-last-of-type-pseudo>:nth-last-of-type() pseudo-class</a></h5>
1773
1774 <p>The <code>:nth-last-of-type(<var>a</var>n+<var>b</var>)</code>
1775 pseudo-class notation represents an element that has
1776 <var>a</var><code>n</code>+<var>b</var>-1 siblings with the same
1777 element name <strong>after</strong> it in the document tree, for a
1778 given zero or positive integer value of <code>n</code>, and has a
1779 parent element. See <code>:nth-child()</code> pseudo-class for the
1780 syntax of its argument. It also accepts the '<code>even</code>' and '<code>odd</ code>' values.
1781
1782
1783 <div class="example">
1784 <p>Example:</p>
1785 <p>To represent all <code>h2</code> children of an XHTML
1786 <code>body</code> except the first and last, one could use the
1787 following selector:</p>
1788 <pre>body &gt; h2:nth-of-type(n+2):nth-last-of-type(n+2)</pre>
1789 <p>In this case, one could also use <code>:not()</code>, although the
1790 selector ends up being just as long:</p>
1791 <pre>body &gt; h2:not(:first-of-type):not(:last-of-type)</pre>
1792 </div>
1793
1794
1795 <h5><a name=first-child-pseudo>:first-child pseudo-class</a></h5>
1796
1797 <p>Same as <code>:nth-child(1)</code>. The <code>:first-child</code> pseudo-clas s
1798 represents an element that is the first child of some other element.
1799
1800
1801 <div class="example">
1802 <p>Examples:</p>
1803 <p>The following selector represents a <code>p</code> element that is
1804 the first child of a <code>div</code> element:</p>
1805 <pre>div &gt; p:first-child</pre>
1806 <p>This selector can represent the <code>p</code> inside the
1807 <code>div</code> of the following fragment:</p>
1808 <pre>&lt;p&gt; The last P before the note.&lt;/p&gt;
1809 &lt;div class="note"&gt;
1810 &lt;p&gt; The first P inside the note.&lt;/p&gt;
1811 &lt;/div&gt;</pre>but cannot represent the second <code>p</code> in the followin g
1812 fragment:
1813 <pre>&lt;p&gt; The last P before the note.&lt;/p&gt;
1814 &lt;div class="note"&gt;
1815 &lt;h2&gt; Note &lt;/h2&gt;
1816 &lt;p&gt; The first P inside the note.&lt;/p&gt;
1817 &lt;/div&gt;</pre>
1818 <p>The following two selectors are usually equivalent:</p>
1819 <pre>* &gt; a:first-child /* a is first child of any element */
1820 a:first-child /* Same (assuming a is not the root element) */</pre>
1821 </div>
1822
1823 <h5><a name=last-child-pseudo>:last-child pseudo-class</a></h5>
1824
1825 <p>Same as <code>:nth-last-child(1)</code>. The <code>:last-child</code> pseudo- class
1826 represents an element that is the last child of some other element.
1827
1828 <div class="example">
1829 <p>Example:</p>
1830 <p>The following selector represents a list item <code>li</code> that
1831 is the last child of an ordered list <code>ol</code>.
1832 <pre>ol &gt; li:last-child</pre>
1833 </div>
1834
1835 <h5><a name=first-of-type-pseudo>:first-of-type pseudo-class</a></h5>
1836
1837 <p>Same as <code>:nth-of-type(1)</code>. The <code>:first-of-type</code> pseudo- class
1838 represents an element that is the first sibling of its type in the list of
1839 children of its parent element.
1840
1841 <div class="example">
1842 <p>Example:</p>
1843 <p>The following selector represents a definition title
1844 <code>dt</code> inside a definition list <code>dl</code>, this
1845 <code>dt</code> being the first of its type in the list of children of
1846 its parent element.</p>
1847 <pre>dl dt:first-of-type</pre>
1848 <p>It is a valid description for the first two <code>dt</code>
1849 elements in the following example but not for the third one:</p>
1850 <pre>&lt;dl&gt;
1851 &lt;dt&gt;gigogne&lt;/dt&gt;
1852 &lt;dd&gt;
1853 &lt;dl&gt;
1854 &lt;dt&gt;fus&eacute;e&lt;/dt&gt;
1855 &lt;dd&gt;multistage rocket&lt;/dd&gt;
1856 &lt;dt&gt;table&lt;/dt&gt;
1857 &lt;dd&gt;nest of tables&lt;/dd&gt;
1858 &lt;/dl&gt;
1859 &lt;/dd&gt;
1860 &lt;/dl&gt;</pre>
1861 </div>
1862
1863 <h5><a name=last-of-type-pseudo>:last-of-type pseudo-class</a></h5>
1864
1865 <p>Same as <code>:nth-last-of-type(1)</code>. The
1866 <code>:last-of-type</code> pseudo-class represents an element that is
1867 the last sibling of its type in the list of children of its parent
1868 element.</p>
1869
1870 <div class="example">
1871 <p>Example:</p>
1872 <p>The following selector represents the last data cell
1873 <code>td</code> of a table row.</p>
1874 <pre>tr &gt; td:last-of-type</pre>
1875 </div>
1876
1877 <h5><a name=only-child-pseudo>:only-child pseudo-class</a></h5>
1878
1879 <p>Represents an element that has a parent element and whose parent
1880 element has no other element children. Same as
1881 <code>:first-child:last-child</code> or
1882 <code>:nth-child(1):nth-last-child(1)</code>, but with a lower
1883 specificity.</p>
1884
1885 <h5><a name=only-of-type-pseudo>:only-of-type pseudo-class</a></h5>
1886
1887 <p>Represents an element that has a parent element and whose parent
1888 element has no other element children with the same element name. Same
1889 as <code>:first-of-type:last-of-type</code> or
1890 <code>:nth-of-type(1):nth-last-of-type(1)</code>, but with a lower
1891 specificity.</p>
1892
1893
1894 <h5><a name=empty-pseudo></a>:empty pseudo-class</h5>
1895
1896 <p>The <code>:empty</code> pseudo-class represents an element that has
1897 no children at all. In terms of the DOM, only element nodes and text
1898 nodes (including CDATA nodes and entity references) whose data has a
1899 non-zero length must be considered as affecting emptiness; comments,
1900 PIs, and other nodes must not affect whether an element is considered
1901 empty or not.</p>
1902
1903 <div class="example">
1904 <p>Examples:</p>
1905 <p><code>p:empty</code> is a valid representation of the following fragment:</p >
1906 <pre>&lt;p&gt;&lt;/p&gt;</pre>
1907 <p><code>foo:empty</code> is not a valid representation for the
1908 following fragments:</p>
1909 <pre>&lt;foo&gt;bar&lt;/foo&gt;</pre>
1910 <pre>&lt;foo&gt;&lt;bar&gt;bla&lt;/bar&gt;&lt;/foo&gt;</pre>
1911 <pre>&lt;foo&gt;this is not &lt;bar&gt;:empty&lt;/bar&gt;&lt;/foo&gt;</pre>
1912 </div>
1913
1914 <h4><a name=content-selectors>6.6.6. Blank</a></h4> <!-- It's the Return of Appe ndix H!!! Run away! -->
1915
1916 <p>This section intentionally left blank.</p>
1917 <!-- (used to be :contains()) -->
1918
1919 <h4><a name=negation></a>6.6.7. The negation pseudo-class</h4>
1920
1921 <p>The negation pseudo-class, <code>:not(<var>X</var>)</code>, is a
1922 functional notation taking a <a href="#simple-selectors-dfn">simple
1923 selector</a> (excluding the negation pseudo-class itself and
1924 pseudo-elements) as an argument. It represents an element that is not
1925 represented by the argument.
1926
1927 <!-- pseudo-elements are not simple selectors, so the above paragraph
1928 may be a bit confusing -->
1929
1930 <div class="example">
1931 <p>Examples:</p>
1932 <p>The following CSS selector matches all <code>button</code>
1933 elements in an HTML document that are not disabled.</p>
1934 <pre>button:not([DISABLED])</pre>
1935 <p>The following selector represents all but <code>FOO</code>
1936 elements.</p>
1937 <pre>*:not(FOO)</pre>
1938 <p>The following group of selectors represents all HTML elements
1939 except links.</p>
1940 <pre>html|*:not(:link):not(:visited)</pre>
1941 </div>
1942
1943 <p>Default namespace declarations do not affect the argument of the
1944 negation pseudo-class unless the argument is a universal selector or a
1945 type selector.</p>
1946
1947 <div class="example">
1948 <p>Examples:</p>
1949 <p>Assuming that the default namespace is bound to
1950 "http://example.com/", the following selector represents all
1951 elements that are not in that namespace:</p>
1952 <pre>*|*:not(*)</pre>
1953 <p>The following CSS selector matches any element being hovered,
1954 regardless of its namespace. In particular, it is not limited to
1955 only matching elements in the default namespace that are not being
1956 hovered, and elements not in the default namespace don't match the
1957 rule when they <em>are</em> being hovered.</p>
1958 <pre>*|*:not(:hover)</pre>
1959 </div>
1960
1961 <p class="note"><strong>Note</strong>: the :not() pseudo allows
1962 useless selectors to be written. For instance <code>:not(*|*)</code>,
1963 which represents no element at all, or <code>foo:not(bar)</code>,
1964 which is equivalent to <code>foo</code> but with a higher
1965 specificity.</p>
1966
1967 <h3><a name=pseudo-elements>7. Pseudo-elements</a></h3>
1968
1969 <p>Pseudo-elements create abstractions about the document tree beyond
1970 those specified by the document language. For instance, document
1971 languages do not offer mechanisms to access the first letter or first
1972 line of an element's content. Pseudo-elements allow designers to refer
1973 to this otherwise inaccessible information. Pseudo-elements may also
1974 provide designers a way to refer to content that does not exist in the
1975 source document (e.g., the <code>::before</code> and
1976 <code>::after</code> pseudo-elements give access to generated
1977 content).</p>
1978
1979 <p>A pseudo-element is made of two colons (<code>::</code>) followed
1980 by the name of the pseudo-element.</p>
1981
1982 <p>This <code>::</code> notation is introduced by the current document
1983 in order to establish a discrimination between pseudo-classes and
1984 pseudo-elements. For compatibility with existing style sheets, user
1985 agents must also accept the previous one-colon notation for
1986 pseudo-elements introduced in CSS levels 1 and 2 (namely,
1987 <code>:first-line</code>, <code>:first-letter</code>,
1988 <code>:before</code> and <code>:after</code>). This compatibility is
1989 not allowed for the new pseudo-elements introduced in CSS level 3.</p>
1990
1991 <p>Only one pseudo-element may appear per selector, and if present it
1992 must appear after the sequence of simple selectors that represents the
1993 <a href="#subject">subjects</a> of the selector. <span class="note">A
1994 future version of this specification may allow multiple
1995 pesudo-elements per selector.</span></p>
1996
1997 <h4><a name=first-line>7.1. The ::first-line pseudo-element</a></h4>
1998
1999 <p>The <code>::first-line</code> pseudo-element describes the contents
2000 of the first formatted line of an element.
2001
2002 <div class="example">
2003 <p>CSS example:</p>
2004 <pre>p::first-line { text-transform: uppercase }</pre>
2005 <p>The above rule means "change the letters of the first line of every
2006 paragraph to uppercase".</p>
2007 </div>
2008
2009 <p>The selector <code>p::first-line</code> does not match any real
2010 HTML element. It does match a pseudo-element that conforming user
2011 agents will insert at the beginning of every paragraph.</p>
2012
2013 <p>Note that the length of the first line depends on a number of
2014 factors, including the width of the page, the font size, etc. Thus,
2015 an ordinary HTML paragraph such as:</p>
2016
2017 <pre>
2018 &lt;P&gt;This is a somewhat long HTML
2019 paragraph that will be broken into several
2020 lines. The first line will be identified
2021 by a fictional tag sequence. The other lines
2022 will be treated as ordinary lines in the
2023 paragraph.&lt;/P&gt;
2024 </pre>
2025
2026 <p>the lines of which happen to be broken as follows:
2027
2028 <pre>
2029 THIS IS A SOMEWHAT LONG HTML PARAGRAPH THAT
2030 will be broken into several lines. The first
2031 line will be identified by a fictional tag
2032 sequence. The other lines will be treated as
2033 ordinary lines in the paragraph.
2034 </pre>
2035
2036 <p>This paragraph might be "rewritten" by user agents to include the
2037 <em>fictional tag sequence</em> for <code>::first-line</code>. This
2038 fictional tag sequence helps to show how properties are inherited.</p>
2039
2040 <pre>
2041 &lt;P&gt;<b>&lt;P::first-line&gt;</b> This is a somewhat long HTML
2042 paragraph that <b>&lt;/P::first-line&gt;</b> will be broken into several
2043 lines. The first line will be identified
2044 by a fictional tag sequence. The other lines
2045 will be treated as ordinary lines in the
2046 paragraph.&lt;/P&gt;
2047 </pre>
2048
2049 <p>If a pseudo-element breaks up a real element, the desired effect
2050 can often be described by a fictional tag sequence that closes and
2051 then re-opens the element. Thus, if we mark up the previous paragraph
2052 with a <code>span</code> element:</p>
2053
2054 <pre>
2055 &lt;P&gt;<b>&lt;SPAN class="test"&gt;</b> This is a somewhat long HTML
2056 paragraph that will be broken into several
2057 lines.<b>&lt;/SPAN&gt;</b> The first line will be identified
2058 by a fictional tag sequence. The other lines
2059 will be treated as ordinary lines in the
2060 paragraph.&lt;/P&gt;
2061 </pre>
2062
2063 <p>the user agent could simulate start and end tags for
2064 <code>span</code> when inserting the fictional tag sequence for
2065 <code>::first-line</code>.
2066
2067 <pre>
2068 &lt;P&gt;&lt;P::first-line&gt;<b>&lt;SPAN class="test"&gt;</b> This is a
2069 somewhat long HTML
2070 paragraph that will <b>&lt;/SPAN&gt;</b>&lt;/P::first-line&gt;<b>&lt;SPAN class= "test"&gt;</b> be
2071 broken into several
2072 lines.<b>&lt;/SPAN&gt;</b> The first line will be identified
2073 by a fictional tag sequence. The other lines
2074 will be treated as ordinary lines in the
2075 paragraph.&lt;/P&gt;
2076 </pre>
2077
2078 <p>In CSS, the <code>::first-line</code> pseudo-element can only be
2079 attached to a block-level element, an inline-block, a table-caption,
2080 or a table-cell.</p>
2081
2082 <p><a name="first-formatted-line"></a>The "first formatted line" of an
2083 element may occur inside a
2084 block-level descendant in the same flow (i.e., a block-level
2085 descendant that is not positioned and not a float). E.g., the first
2086 line of the <code>div</code> in <code>&lt;DIV>&lt;P>This
2087 line...&lt;/P>&lt/DIV></code> is the first line of the <code>p</code> (assuming
2088 that both <code>p</code> and <code>div</code> are block-level).
2089
2090 <p>The first line of a table-cell or inline-block cannot be the first
2091 formatted line of an ancestor element. Thus, in <code>&lt;DIV&gt;&lt;P
2092 STYLE="display: inline-block">Hello&lt;BR&gt;Goodbye&lt;/P&gt;
2093 etcetera&lt;/DIV&gt;</code> the first formatted line of the
2094 <code>div</code> is not the line "Hello".
2095
2096 <p class="note">Note that the first line of the <code>p</code> in this
2097 fragment: <code>&lt;p&gt&lt;br&gt;First...</code> doesn't contain any
2098 letters (assuming the default style for <code>br</code> in HTML
2099 4). The word "First" is not on the first formatted line.
2100
2101 <p>A UA should act as if the fictional start tags of the
2102 <code>::first-line</code> pseudo-elements were nested just inside the
2103 innermost enclosing block-level element. (Since CSS1 and CSS2 were
2104 silent on this case, authors should not rely on this behavior.) Here
2105 is an example. The fictional tag sequence for</p>
2106
2107 <pre>
2108 &lt;DIV>
2109 &lt;P>First paragraph&lt;/P>
2110 &lt;P>Second paragraph&lt;/P>
2111 &lt;/DIV>
2112 </pre>
2113
2114 <p>is</p>
2115
2116 <pre>
2117 &lt;DIV>
2118 &lt;P>&lt;DIV::first-line>&lt;P::first-line>First paragraph&lt;/P::first-line> &lt;/DIV::first-line>&lt;/P>
2119 &lt;P>&lt;P::first-line>Second paragraph&lt;/P::first-line>&lt;/P>
2120 &lt;/DIV>
2121 </pre>
2122
2123 <p>The <code>::first-line</code> pseudo-element is similar to an
2124 inline-level element, but with certain restrictions. In CSS, the
2125 following properties apply to a <code>::first-line</code>
2126 pseudo-element: font properties, color property, background
2127 properties, 'word-spacing', 'letter-spacing', 'text-decoration',
2128 'vertical-align', 'text-transform', 'line-height'. UAs may apply other
2129 properties as well.</p>
2130
2131
2132 <h4><a name=first-letter>7.2. The ::first-letter pseudo-element</a></h4>
2133
2134 <p>The <code>::first-letter</code> pseudo-element represents the first
2135 letter of the first line of a block, if it is not preceded by any
2136 other content (such as images or inline tables) on its line. The
2137 ::first-letter pseudo-element may be used for "initial caps" and "drop
2138 caps", which are common typographical effects. This type of initial
2139 letter is similar to an inline-level element if its 'float' property
2140 is 'none'; otherwise, it is similar to a floated element.</p>
2141
2142 <p>In CSS, these are the properties that apply to <code>::first-letter</code>
2143 pseudo-elements: font properties, 'text-decoration', 'text-transform',
2144 'letter-spacing', 'word-spacing' (when appropriate), 'line-height',
2145 'float', 'vertical-align' (only if 'float' is 'none'), margin
2146 properties, padding properties, border properties, color property,
2147 background properties. UAs may apply other properties as well. To
2148 allow UAs to render a typographically correct drop cap or initial cap,
2149 the UA may choose a line-height, width and height based on the shape
2150 of the letter, unlike for normal elements.</p>
2151
2152 <div class="example">
2153 <p>Example:</p>
2154 <p>This example shows a possible rendering of an initial cap. Note
2155 that the 'line-height' that is inherited by the <code>::first-letter</code>
2156 pseudo-element is 1.1, but the UA in this example has computed the
2157 height of the first letter differently, so that it doesn't cause any
2158 unnecessary space between the first two lines. Also note that the
2159 fictional start tag of the first letter is inside the <span>span</span>, and thu s
2160 the font weight of the first letter is normal, not bold as the <span>span</span> :
2161 <pre>
2162 p { line-height: 1.1 }
2163 p::first-letter { font-size: 3em; font-weight: normal }
2164 span { font-weight: bold }
2165 ...
2166 &lt;p>&lt;span>Het hemelsche&lt;/span> gerecht heeft zich ten lange lesten&lt;br >
2167 Erbarremt over my en mijn benaeuwde vesten&lt;br>
2168 En arme burgery, en op mijn volcx gebed&lt;br>
2169 En dagelix geschrey de bange stad ontzet.
2170 </pre>
2171 <div class="figure">
2172 <p><img src="initial-cap.png" alt="Image illustrating the ::first-letter pseudo- element">
2173 </div>
2174 </div>
2175
2176 <div class="example">
2177 <p>The following CSS will make a drop cap initial letter span about two lines:</ p>
2178
2179 <pre>
2180 &lt;!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"&gt;
2181 &lt;HTML&gt;
2182 &lt;HEAD&gt;
2183 &lt;TITLE&gt;Drop cap initial letter&lt;/TITLE&gt;
2184 &lt;STYLE type="text/css"&gt;
2185 P { font-size: 12pt; line-height: 1.2 }
2186 P::first-letter { font-size: 200%; font-weight: bold; float: left }
2187 SPAN { text-transform: uppercase }
2188 &lt;/STYLE&gt;
2189 &lt;/HEAD&gt;
2190 &lt;BODY&gt;
2191 &lt;P&gt;&lt;SPAN&gt;The first&lt;/SPAN&gt; few words of an article
2192 in The Economist.&lt;/P&gt;
2193 &lt;/BODY&gt;
2194 &lt;/HTML&gt;
2195 </pre>
2196
2197 <p>This example might be formatted as follows:</p>
2198
2199 <div class="figure">
2200 <P><img src="first-letter.gif" alt="Image illustrating the combined effect of th e ::first-letter and ::first-line pseudo-elements"></p>
2201 </div>
2202
2203 <p>The <span class="index-inst" title="fictional tag
2204 sequence">fictional tag sequence</span> is:</p>
2205
2206 <pre>
2207 &lt;P&gt;
2208 &lt;SPAN&gt;
2209 &lt;P::first-letter&gt;
2210 T
2211 &lt;/P::first-letter&gt;he first
2212 &lt;/SPAN&gt;
2213 few words of an article in the Economist.
2214 &lt;/P&gt;
2215 </pre>
2216
2217 <p>Note that the <code>::first-letter</code> pseudo-element tags abut
2218 the content (i.e., the initial character), while the ::first-line
2219 pseudo-element start tag is inserted right after the start tag of the
2220 block element.</p> </div>
2221
2222 <p>In order to achieve traditional drop caps formatting, user agents
2223 may approximate font sizes, for example to align baselines. Also, the
2224 glyph outline may be taken into account when formatting.</p>
2225
2226 <p>Punctuation (i.e, characters defined in Unicode in the "open" (Ps),
2227 "close" (Pe), "initial" (Pi). "final" (Pf) and "other" (Po)
2228 punctuation classes), that precedes or follows the first letter should
2229 be included. <a href="#refsUNICODE">[UNICODE]</a></p>
2230
2231 <div class="figure">
2232 <P><img src="first-letter2.gif" alt="Quotes that precede the
2233 first letter should be included."></p>
2234 </div>
2235
2236 <p>The <code>::first-letter</code> also applies if the first letter is
2237 in fact a digit, e.g., the "6" in "67 million dollars is a lot of
2238 money."</p>
2239
2240 <p>In CSS, the <code>::first-letter</code> pseudo-element applies to
2241 block, list-item, table-cell, table-caption, and inline-block
2242 elements. <span class="note">A future version of this specification
2243 may allow this pesudo-element to apply to more element
2244 types.</span></p>
2245
2246 <p>The <code>::first-letter</code> pseudo-element can be used with all
2247 such elements that contain text, or that have a descendant in the same
2248 flow that contains text. A UA should act as if the fictional start tag
2249 of the ::first-letter pseudo-element is just before the first text of
2250 the element, even if that first text is in a descendant.</p>
2251
2252 <div class="example">
2253 <p>Example:</p>
2254 <p>The fictional tag sequence for this HTMLfragment:
2255 <pre>&lt;div>
2256 &lt;p>The first text.</pre>
2257 <p>is:
2258 <pre>&lt;div>
2259 &lt;p>&lt;div::first-letter>&lt;p::first-letter>T&lt;/...>&lt;/...>he first text .</pre>
2260 </div>
2261
2262 <p>The first letter of a table-cell or inline-block cannot be the
2263 first letter of an ancestor element. Thus, in <code>&lt;DIV&gt;&lt;P
2264 STYLE="display: inline-block">Hello&lt;BR&gt;Goodbye&lt;/P&gt;
2265 etcetera&lt;/DIV&gt;</code> the first letter of the <code>div</code> is not the
2266 letter "H". In fact, the <code>div</code> doesn't have a first letter.
2267
2268 <p>The first letter must occur on the <a
2269 href="#first-formatted-line">first formatted line.</a> For example, in
2270 this fragment: <code>&lt;p&gt&lt;br&gt;First...</code> the first line
2271 doesn't contain any letters and <code>::first-letter</code> doesn't
2272 match anything (assuming the default style for <code>br</code> in HTML
2273 4). In particular, it does not match the "F" of "First."
2274
2275 <p>In CSS, if an element is a list item ('display: list-item'), the
2276 <code>::first-letter</code> applies to the first letter in the
2277 principal box after the marker. UAs may ignore
2278 <code>::first-letter</code> on list items with 'list-style-position:
2279 inside'. If an element has <code>::before</code> or
2280 <code>::after</code> content, the <code>::first-letter</code> applies
2281 to the first letter of the element <em>including</em> that content.
2282
2283 <div class="example">
2284 <p>Example:</p>
2285 <p>After the rule 'p::before {content: "Note: "}', the selector
2286 'p::first-letter' matches the "N" of "Note".</p>
2287 </div>
2288
2289 <p>Some languages may have specific rules about how to treat certain
2290 letter combinations. In Dutch, for example, if the letter combination
2291 "ij" appears at the beginning of a word, both letters should be
2292 considered within the <code>::first-letter</code> pseudo-element.
2293
2294 <p>If the letters that would form the ::first-letter are not in the
2295 same element, such as "'T" in <code>&lt;p>'&lt;em>T...</code>, the UA
2296 may create a ::first-letter pseudo-element from one of the elements,
2297 both elements, or simply not create a pseudo-element.</p>
2298
2299 <p>Similarly, if the first letter(s) of the block are not at the start
2300 of the line (for example due to bidirectional reordering), then the UA
2301 need not create the pseudo-element(s).
2302
2303 <div class="example">
2304 <p>Example:</p>
2305 <p><a name="overlapping-example">The following example</a> illustrates
2306 how overlapping pseudo-elements may interact. The first letter of
2307 each P element will be green with a font size of '24pt'. The rest of
2308 the first formatted line will be 'blue' while the rest of the
2309 paragraph will be 'red'.</p>
2310
2311 <pre>p { color: red; font-size: 12pt }
2312 p::first-letter { color: green; font-size: 200% }
2313 p::first-line { color: blue }
2314
2315 &lt;P&gt;Some text that ends up on two lines&lt;/P&gt;</pre>
2316
2317 <p>Assuming that a line break will occur before the word "ends", the
2318 <span class="index-inst" title="fictional tag sequence">fictional tag
2319 sequence</span> for this fragment might be:</p>
2320
2321 <pre>&lt;P&gt;
2322 &lt;P::first-line&gt;
2323 &lt;P::first-letter&gt;
2324 S
2325 &lt;/P::first-letter&gt;ome text that
2326 &lt;/P::first-line&gt;
2327 ends up on two lines
2328 &lt;/P&gt;</pre>
2329
2330 <p>Note that the <code>::first-letter</code> element is inside the <code>::first -line</code>
2331 element. Properties set on <code>::first-line</code> are inherited by
2332 <code>::first-letter</code>, but are overridden if the same property is set on
2333 <code>::first-letter</code>.</p>
2334 </div>
2335
2336
2337 <h4><a name=UIfragments>7.3.</a> <a name=selection>The ::selection pseudo-elemen t</a></h4>
2338
2339 <p>The <code>::selection</code> pseudo-element applies to the portion
2340 of a document that has been highlighted by the user. This also
2341 applies, for example, to selected text within an editable text
2342 field. This pseudo-element should not be confused with the <code><a
2343 href="#checked">:checked</a></code> pseudo-class (which used to be
2344 named <code>:selected</code>)
2345
2346 <p>Although the <code>::selection</code> pseudo-element is dynamic in
2347 nature, and is altered by user action, it is reasonable to expect that
2348 when a UA re-renders to a static medium (such as a printed page, see
2349 <a href="#refsCSS21">[CSS21]</a>) which was originally rendered to a
2350 dynamic medium (like screen), the UA may wish to transfer the current
2351 <code>::selection</code> state to that other medium, and have all the
2352 appropriate formatting and rendering take effect as well. This is not
2353 required &mdash; UAs may omit the <code>::selection</code>
2354 pseudo-element for static media.
2355
2356 <p>These are the CSS properties that apply to <code>::selection</code>
2357 pseudo-elements: color, background, cursor (optional), outline
2358 (optional). The computed value of the 'background-image' property on
2359 <code>::selection</code> may be ignored.
2360
2361
2362 <h4><a name=gen-content>7.4. The ::before and ::after pseudo-elements</a></h4>
2363
2364 <p>The <code>::before</code> and <code>::after</code> pseudo-elements
2365 can be used to describe generated content before or after an element's
2366 content. They are explained in CSS 2.1 <a
2367 href="#refsCSS21">[CSS21]</a>.</p>
2368
2369 <p>When the <code>::first-letter</code> and <code>::first-line</code>
2370 pseudo-elements are combined with <code>::before</code> and
2371 <code>::after</code>, they apply to the first letter or line of the
2372 element including the inserted text.</p>
2373
2374 <h2><a name=combinators>8. Combinators</a></h2>
2375
2376 <h3><a name=descendant-combinators>8.1. Descendant combinator</a></h3>
2377
2378 <p>At times, authors may want selectors to describe an element that is
2379 the descendant of another element in the document tree (e.g., "an
2380 <code>EM</code> element that is contained within an <code>H1</code>
2381 element"). Descendant combinators express such a relationship. A
2382 descendant combinator is <a href="#whitespace">white space</a> that
2383 separates two sequences of simple selectors. A selector of the form
2384 "<code>A B</code>" represents an element <code>B</code> that is an
2385 arbitrary descendant of some ancestor element <code>A</code>.
2386
2387 <div class="example">
2388 <p>Examples:</p>
2389 <p>For example, consider the following selector:</p>
2390 <pre>h1 em</pre>
2391 <p>It represents an <code>em</code> element being the descendant of
2392 an <code>h1</code> element. It is a correct and valid, but partial,
2393 description of the following fragment:</p>
2394 <pre>&lt;h1&gt;This &lt;span class="myclass"&gt;headline
2395 is &lt;em&gt;very&lt;/em&gt; important&lt;/span&gt;&lt;/h1&gt;</pre>
2396 <p>The following selector:</p>
2397 <pre>div * p</pre>
2398 <p>represents a <code>p</code> element that is a grandchild or later
2399 descendant of a <code>div</code> element. Note the whitespace on
2400 either side of the "*" is not part of the universal selector; the
2401 whitespace is a combinator indicating that the DIV must be the
2402 ancestor of some element, and that that element must be an ancestor
2403 of the P.</p>
2404 <p>The following selector, which combines descendant combinators and
2405 <a href="#attribute-selectors">attribute selectors</a>, represents an
2406 element that (1) has the <code>href</code> attribute set and (2) is
2407 inside a <code>p</code> that is itself inside a <code>div</code>:</p>
2408 <pre>div p *[href]</pre>
2409 </div>
2410
2411 <h3><a name=child-combinators>8.2. Child combinators</a></h3>
2412
2413 <p>A <dfn>child combinator</dfn> describes a childhood relationship
2414 between two elements. A child combinator is made of the
2415 &quot;greater-than sign&quot; (<code>&gt;</code>) character and
2416 separates two sequences of simple selectors.
2417
2418
2419 <div class="example">
2420 <p>Examples:</p>
2421 <p>The following selector represents a <code>p</code> element that is
2422 child of <code>body</code>:</p>
2423 <pre>body &gt; p</pre>
2424 <p>The following example combines descendant combinators and child
2425 combinators.</p>
2426 <pre>div ol&gt;li p</pre><!-- LEAVE THOSE SPACES OUT! see below -->
2427 <p>It represents a <code>p</code> element that is a descendant of an
2428 <code>li</code> element; the <code>li</code> element must be the
2429 child of an <code>ol</code> element; the <code>ol</code> element must
2430 be a descendant of a <code>div</code>. Notice that the optional white
2431 space around the "&gt;" combinator has been left out.</p>
2432 </div>
2433
2434 <p>For information on selecting the first child of an element, please
2435 see the section on the <code><a
2436 href="#structural-pseudos">:first-child</a></code> pseudo-class
2437 above.</p>
2438
2439 <h3><a name=sibling-combinators>8.3. Sibling combinators</a></h3>
2440
2441 <p>There are two different sibling combinators: the adjacent sibling
2442 combinator and the general sibling combinator. In both cases,
2443 non-element nodes (e.g. text between elements) are ignored when
2444 considering adjacency of elements.</p>
2445
2446 <h4><a name=adjacent-sibling-combinators>8.3.1. Adjacent sibling combinator</a>< /h4>
2447
2448 <p>The adjacent sibling combinator is made of the &quot;plus
2449 sign&quot; (U+002B, <code>+</code>) character that separates two
2450 sequences of simple selectors. The elements represented by the two
2451 sequences share the same parent in the document tree and the element
2452 represented by the first sequence immediately precedes the element
2453 represented by the second one.</p>
2454
2455 <div class="example">
2456 <p>Examples:</p>
2457 <p>The following selector represents a <code>p</code> element
2458 immediately following a <code>math</code> element:</p>
2459 <pre>math + p</pre>
2460 <p>The following selector is conceptually similar to the one in the
2461 previous example, except that it adds an attribute selector &mdash; it
2462 adds a constraint to the <code>h1</code> element, that it must have
2463 <code>class="opener"</code>:</p>
2464 <pre>h1.opener + h2</pre>
2465 </div>
2466
2467
2468 <h4><a name=general-sibling-combinators>8.3.2. General sibling combinator</a></h 4>
2469
2470 <p>The general sibling combinator is made of the &quot;tilde&quot;
2471 (U+007E, <code>~</code>) character that separates two sequences of
2472 simple selectors. The elements represented by the two sequences share
2473 the same parent in the document tree and the element represented by
2474 the first sequence precedes (not necessarily immediately) the element
2475 represented by the second one.</p>
2476
2477 <div class="example">
2478 <p>Example:</p>
2479 <pre>h1 ~ pre</pre>
2480 <p>represents a <code>pre</code> element following an <code>h1</code>. It
2481 is a correct and valid, but partial, description of:</p>
2482 <pre>&lt;h1&gt;Definition of the function a&lt;/h1&gt;
2483 &lt;p&gt;Function a(x) has to be applied to all figures in the table.&lt;/p&gt;
2484 &lt;pre&gt;function a(x) = 12x/13.5&lt;/pre&gt;</pre>
2485 </div>
2486
2487 <h2><a name=specificity>9. Calculating a selector's specificity</a></h2>
2488
2489 <p>A selector's specificity is calculated as follows:</p>
2490
2491 <ul>
2492 <li>count the number of ID selectors in the selector (= a)</li>
2493 <li>count the number of class selectors, attributes selectors, and pseudo-clas ses in the selector (= b)</li>
2494 <li>count the number of element names in the selector (= c)</li>
2495 <li>ignore pseudo-elements</li>
2496 </ul>
2497
2498 <p>Selectors inside <a href="#negation">the negation pseudo-class</a>
2499 are counted like any other, but the negation itself does not count as
2500 a pseudo-class.</p>
2501
2502 <p>Concatenating the three numbers a-b-c (in a number system with a
2503 large base) gives the specificity.</p>
2504
2505 <div class="example">
2506 <p>Examples:</p>
2507 <pre>* /* a=0 b=0 c=0 -&gt; specificity = 0 */
2508 LI /* a=0 b=0 c=1 -&gt; specificity = 1 */
2509 UL LI /* a=0 b=0 c=2 -&gt; specificity = 2 */
2510 UL OL+LI /* a=0 b=0 c=3 -&gt; specificity = 3 */
2511 H1 + *[REL=up] /* a=0 b=1 c=1 -&gt; specificity = 11 */
2512 UL OL LI.red /* a=0 b=1 c=3 -&gt; specificity = 13 */
2513 LI.red.level /* a=0 b=2 c=1 -&gt; specificity = 21 */
2514 #x34y /* a=1 b=0 c=0 -&gt; specificity = 100 */
2515 #s12:not(FOO) /* a=1 b=0 c=1 -&gt; specificity = 101 */
2516 </pre>
2517 </div>
2518
2519 <p class="note"><strong>Note:</strong> the specificity of the styles
2520 specified in an HTML <code>style</code> attribute is described in CSS
2521 2.1. <a href="#refsCSS21">[CSS21]</a>.</p>
2522
2523 <h2><a name=w3cselgrammar>10. The grammar of Selectors</a></h2>
2524
2525 <h3><a name=grammar>10.1. Grammar</a></h3>
2526
2527 <p>The grammar below defines the syntax of Selectors. It is globally
2528 LL(1) and can be locally LL(2) (but note that most UA's should not use
2529 it directly, since it doesn't express the parsing conventions). The
2530 format of the productions is optimized for human consumption and some
2531 shorthand notations beyond Yacc (see <a href="#refsYACC">[YACC]</a>)
2532 are used:</p>
2533
2534 <ul>
2535 <li><b>*</b>: 0 or more
2536 <li><b>+</b>: 1 or more
2537 <li><b>?</b>: 0 or 1
2538 <li><b>|</b>: separates alternatives
2539 <li><b>[ ]</b>: grouping </li>
2540 </ul>
2541
2542 <p>The productions are:</p>
2543
2544 <pre>selectors_group
2545 : selector [ COMMA S* selector ]*
2546 ;
2547
2548 selector
2549 : simple_selector_sequence [ combinator simple_selector_sequence ]*
2550 ;
2551
2552 combinator
2553 /* combinators can be surrounded by white space */
2554 : PLUS S* | GREATER S* | TILDE S* | S+
2555 ;
2556
2557 simple_selector_sequence
2558 : [ type_selector | universal ]
2559 [ HASH | class | attrib | pseudo | negation ]*
2560 | [ HASH | class | attrib | pseudo | negation ]+
2561 ;
2562
2563 type_selector
2564 : [ namespace_prefix ]? element_name
2565 ;
2566
2567 namespace_prefix
2568 : [ IDENT | '*' ]? '|'
2569 ;
2570
2571 element_name
2572 : IDENT
2573 ;
2574
2575 universal
2576 : [ namespace_prefix ]? '*'
2577 ;
2578
2579 class
2580 : '.' IDENT
2581 ;
2582
2583 attrib
2584 : '[' S* [ namespace_prefix ]? IDENT S*
2585 [ [ PREFIXMATCH |
2586 SUFFIXMATCH |
2587 SUBSTRINGMATCH |
2588 '=' |
2589 INCLUDES |
2590 DASHMATCH ] S* [ IDENT | STRING ] S*
2591 ]? ']'
2592 ;
2593
2594 pseudo
2595 /* '::' starts a pseudo-element, ':' a pseudo-class */
2596 /* Exceptions: :first-line, :first-letter, :before and :after. */
2597 /* Note that pseudo-elements are restricted to one per selector and */
2598 /* occur only in the last simple_selector_sequence. */
2599 : ':' ':'? [ IDENT | functional_pseudo ]
2600 ;
2601
2602 functional_pseudo
2603 : FUNCTION S* expression ')'
2604 ;
2605
2606 expression
2607 /* In CSS3, the expressions are identifiers, strings, */
2608 /* or of the form "an+b" */
2609 : [ [ PLUS | '-' | DIMENSION | NUMBER | STRING | IDENT ] S* ]+
2610 ;
2611
2612 negation
2613 : NOT S* negation_arg S* ')'
2614 ;
2615
2616 negation_arg
2617 : type_selector | universal | HASH | class | attrib | pseudo
2618 ;</pre>
2619
2620
2621 <h3><a name=lex>10.2. Lexical scanner</a></h3>
2622
2623 <p>The following is the <a name=x3>tokenizer</a>, written in Flex (see
2624 <a href="#refsFLEX">[FLEX]</a>) notation. The tokenizer is
2625 case-insensitive.</p>
2626
2627 <p>The two occurrences of "\377" represent the highest character
2628 number that current versions of Flex can deal with (decimal 255). They
2629 should be read as "\4177777" (decimal 1114111), which is the highest
2630 possible code point in Unicode/ISO-10646. <a
2631 href="#refsUNICODE">[UNICODE]</a></p>
2632
2633 <pre>%option case-insensitive
2634
2635 ident [-]?{nmstart}{nmchar}*
2636 name {nmchar}+
2637 nmstart [_a-z]|{nonascii}|{escape}
2638 nonascii [^\0-\177]
2639 unicode \\[0-9a-f]{1,6}(\r\n|[ \n\r\t\f])?
2640 escape {unicode}|\\[^\n\r\f0-9a-f]
2641 nmchar [_a-z0-9-]|{nonascii}|{escape}
2642 num [0-9]+|[0-9]*\.[0-9]+
2643 string {string1}|{string2}
2644 string1 \"([^\n\r\f\\"]|\\{nl}|{nonascii}|{escape})*\"
2645 string2 \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*\'
2646 invalid {invalid1}|{invalid2}
2647 invalid1 \"([^\n\r\f\\"]|\\{nl}|{nonascii}|{escape})*
2648 invalid2 \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*
2649 nl \n|\r\n|\r|\f
2650 w [ \t\r\n\f]*
2651
2652 %%
2653
2654 [ \t\r\n\f]+ return S;
2655
2656 "~=" return INCLUDES;
2657 "|=" return DASHMATCH;
2658 "^=" return PREFIXMATCH;
2659 "$=" return SUFFIXMATCH;
2660 "*=" return SUBSTRINGMATCH;
2661 {ident} return IDENT;
2662 {string} return STRING;
2663 {ident}"(" return FUNCTION;
2664 {num} return NUMBER;
2665 "#"{name} return HASH;
2666 {w}"+" return PLUS;
2667 {w}"&gt;" return GREATER;
2668 {w}"," return COMMA;
2669 {w}"~" return TILDE;
2670 ":not(" return NOT;
2671 @{ident} return ATKEYWORD;
2672 {invalid} return INVALID;
2673 {num}% return PERCENTAGE;
2674 {num}{ident} return DIMENSION;
2675 "&lt;!--" return CDO;
2676 "--&gt;" return CDC;
2677
2678 "url("{w}{string}{w}")" return URI;
2679 "url("{w}([!#$%&*-~]|{nonascii}|{escape})*{w}")" return URI;
2680 U\+[0-9a-f?]{1,6}(-[0-9a-f]{1,6})? return UNICODE_RANGE;
2681
2682 \/\*[^*]*\*+([^/*][^*]*\*+)*\/ /* ignore comments */
2683
2684 . return *yytext;</pre>
2685
2686
2687
2688 <h2><a name=downlevel>11. Namespaces and down-level clients</a></h2>
2689
2690 <p>An important issue is the interaction of CSS selectors with XML
2691 documents in web clients that were produced prior to this
2692 document. Unfortunately, due to the fact that namespaces must be
2693 matched based on the URI which identifies the namespace, not the
2694 namespace prefix, some mechanism is required to identify namespaces in
2695 CSS by their URI as well. Without such a mechanism, it is impossible
2696 to construct a CSS style sheet which will properly match selectors in
2697 all cases against a random set of XML documents. However, given
2698 complete knowledge of the XML document to which a style sheet is to be
2699 applied, and a limited use of namespaces within the XML document, it
2700 is possible to construct a style sheet in which selectors would match
2701 elements and attributes correctly.</p>
2702
2703 <p>It should be noted that a down-level CSS client will (if it
2704 properly conforms to CSS forward compatible parsing rules) ignore all
2705 <code>@namespace</code> at-rules, as well as all style rules that make
2706 use of namespace qualified element type or attribute selectors. The
2707 syntax of delimiting namespace prefixes in CSS was deliberately chosen
2708 so that down-level CSS clients would ignore the style rules rather
2709 than possibly match them incorrectly.</p>
2710
2711 <p>The use of default namespaces in CSS makes it possible to write
2712 element type selectors that will function in both namespace aware CSS
2713 clients as well as down-level clients. It should be noted that
2714 down-level clients may incorrectly match selectors against XML
2715 elements in other namespaces.</p>
2716
2717 <p>The following are scenarios and examples in which it is possible to
2718 construct style sheets which would function properly in web clients
2719 that do not implement this proposal.</p>
2720
2721 <ol>
2722 <li>
2723
2724 <p>The XML document does not use namespaces.</p>
2725
2726 <ul>
2727
2728 <li>In this case, it is obviously not necessary to declare or use
2729 namespaces in the style sheet. Standard CSS element type and
2730 attribute selectors will function adequately in a down-level
2731 client.</li>
2732
2733 <li>In a CSS namespace aware client, the default behavior of
2734 element selectors matching without regard to namespace will
2735 function properly against all elements, since no namespaces are
2736 present. However, the use of specific element type selectors that
2737 match only elements that have no namespace ("<code>|name</code>")
2738 will guarantee that selectors will match only XML elements that do
2739 not have a declared namespace. </li>
2740
2741 </ul>
2742
2743 </li>
2744
2745 <li>
2746
2747 <p>The XML document defines a single, default namespace used
2748 throughout the document. No namespace prefixes are used in element
2749 names.</p>
2750
2751 <ul>
2752
2753 <li>In this case, a down-level client will function as if
2754 namespaces were not used in the XML document at all. Standard CSS
2755 element type and attribute selectors will match against all
2756 elements. </li>
2757
2758 </ul>
2759
2760 </li>
2761
2762 <li>
2763
2764 <p>The XML document does <b>not</b> use a default namespace, all
2765 namespace prefixes used are known to the style sheet author, and
2766 there is a direct mapping between namespace prefixes and namespace
2767 URIs. (A given prefix may only be mapped to one namespace URI
2768 throughout the XML document; there may be multiple prefixes mapped
2769 to the same URI).</p>
2770
2771 <ul>
2772
2773 <li>In this case, the down-level client will view and match
2774 element type and attribute selectors based on their fully
2775 qualified name, not the local part as outlined in the <a
2776 href="#typenmsp">Type selectors and Namespaces</a> section. CSS
2777 selectors may be declared using an escaped colon "<code>\:</code>"
2778 to describe the fully qualified names, e.g.
2779 "<code>html\:h1</code>" will match
2780 <code>&lt;html:h1&gt;</code>. Selectors using the qualified name
2781 will only match XML elements that use the same prefix. Other
2782 namespace prefixes used in the XML that are mapped to the same URI
2783 will not match as expected unless additional CSS style rules are
2784 declared for them.</li>
2785
2786 <li>Note that selectors declared in this fashion will
2787 <em>only</em> match in down-level clients. A CSS namespace aware
2788 client will match element type and attribute selectors based on
2789 the name's local part. Selectors declared with the fully
2790 qualified name will not match (unless there is no namespace prefix
2791 in the fully qualified name).</li>
2792
2793 </ul>
2794
2795 </li>
2796
2797 </ol>
2798
2799 <p>In other scenarios: when the namespace prefixes used in the XML are
2800 not known in advance by the style sheet author; or a combination of
2801 elements with no namespace are used in conjunction with elements using
2802 a default namespace; or the same namespace prefix is mapped to
2803 <em>different</em> namespace URIs within the same document, or in
2804 different documents; it is impossible to construct a CSS style sheet
2805 that will function properly against all elements in those documents,
2806 unless, the style sheet is written using a namespace URI syntax (as
2807 outlined in this document or similar) and the document is processed by
2808 a CSS and XML namespace aware client.</p>
2809
2810 <h2><a name=profiling>12. Profiles</a></h2>
2811
2812 <p>Each specification using Selectors must define the subset of W3C
2813 Selectors it allows and excludes, and describe the local meaning of
2814 all the components of that subset.</p>
2815
2816 <p>Non normative examples:
2817
2818 <div class="profile">
2819 <table class="tprofile">
2820 <tbody>
2821 <tr>
2822 <th class="title" colspan=2>Selectors profile</th></tr>
2823 <tr>
2824 <th>Specification</th>
2825 <td>CSS level 1</td></tr>
2826 <tr>
2827 <th>Accepts</th>
2828 <td>type selectors<br>class selectors<br>ID selectors<br>:link,
2829 :visited and :active pseudo-classes<br>descendant combinator
2830 <br>::first-line and ::first-letter pseudo-elements</td></tr>
2831 <tr>
2832 <th>Excludes</th>
2833 <td>
2834
2835 <p>universal selector<br>attribute selectors<br>:hover and :focus
2836 pseudo-classes<br>:target pseudo-class<br>:lang() pseudo-class<br>all UI
2837 element states pseudo-classes<br>all structural
2838 pseudo-classes<br>negation pseudo-class<br>all
2839 UI element fragments pseudo-elements<br>::before and ::after
2840 pseudo-elements<br>child combinators<br>sibling combinators
2841
2842 <p>namespaces</td></tr>
2843 <tr>
2844 <th>Extra constraints</th>
2845 <td>only one class selector allowed per sequence of simple
2846 selectors</td></tr></tbody></table><br><br>
2847 <table class="tprofile">
2848 <tbody>
2849 <tr>
2850 <th class="title" colspan=2>Selectors profile</th></tr>
2851 <tr>
2852 <th>Specification</th>
2853 <td>CSS level 2</td></tr>
2854 <tr>
2855 <th>Accepts</th>
2856 <td>type selectors<br>universal selector<br>attribute presence and
2857 values selectors<br>class selectors<br>ID selectors<br>:link, :visited,
2858 :active, :hover, :focus, :lang() and :first-child pseudo-classes
2859 <br>descendant combinator<br>child combinator<br>adjacent sibling
2860 combinator<br>::first-line and ::first-letter pseudo-elements<br>::before
2861 and ::after pseudo-elements</td></tr>
2862 <tr>
2863 <th>Excludes</th>
2864 <td>
2865
2866 <p>content selectors<br>substring matching attribute
2867 selectors<br>:target pseudo-classes<br>all UI element
2868 states pseudo-classes<br>all structural pseudo-classes other
2869 than :first-child<br>negation pseudo-class<br>all UI element
2870 fragments pseudo-elements<br>general sibling combinators
2871
2872 <p>namespaces</td></tr>
2873 <tr>
2874 <th>Extra constraints</th>
2875 <td>more than one class selector per sequence of simple selectors (CSS1
2876 constraint) allowed</td></tr></tbody></table>
2877
2878 <p>In CSS, selectors express pattern matching rules that determine which style
2879 rules apply to elements in the document tree.
2880
2881 <p>The following selector (CSS level 2) will <b>match</b> all anchors <code>a</c ode>
2882 with attribute <code>name</code> set inside a section 1 header <code>h1</code>:
2883 <pre>h1 a[name]</pre>
2884
2885 <p>All CSS declarations attached to such a selector are applied to elements
2886 matching it. </div>
2887
2888 <div class="profile">
2889 <table class="tprofile">
2890 <tbody>
2891 <tr>
2892 <th class="title" colspan=2>Selectors profile</th></tr>
2893 <tr>
2894 <th>Specification</th>
2895 <td>STTS 3</td>
2896 </tr>
2897 <tr>
2898 <th>Accepts</th>
2899 <td>
2900
2901 <p>type selectors<br>universal selectors<br>attribute selectors<br>class
2902 selectors<br>ID selectors<br>all structural pseudo-classes<br>
2903 all combinators
2904
2905 <p>namespaces</td></tr>
2906 <tr>
2907 <th>Excludes</th>
2908 <td>non-accepted pseudo-classes<br>pseudo-elements<br></td></tr>
2909 <tr>
2910 <th>Extra constraints</th>
2911 <td>some selectors and combinators are not allowed in fragment
2912 descriptions on the right side of STTS declarations.</td></tr></tbody></ta ble>
2913 <form>
2914 <input type="text" name="test10"/>
2915 <input type="text" name="foo"/>
2916 <input type="text" name="foo"/>
2917 <input type="text" name="foo"/>
2918 <input type="text" name="foo"/>
2919 <input type="text" name="foo"/>
2920 <input type="text" name="foo"/>
2921 <input type="text" name="foo"/>
2922 <input type="text" name="foo"/>
2923 <input type="text" name="foo"/>
2924 <input type="text" name="foo"/>
2925 <input type="text" name="foo"/>
2926 <input type="text" name="foo"/>
2927 <input type="text" name="foo"/>
2928 <input type="text" name="foo"/>
2929 <input type="text" name="foo"/>
2930 <input type="text" name="foo"/>
2931 <input type="text" name="foo"/>
2932 <input type="text" name="foo"/>
2933 <input type="text" name="foo"/>
2934 <input type="text" name="foo"/>
2935 <input type="text" name="foo"/>
2936 <input type="text" name="foo"/>
2937 <input type="text" name="foo"/>
2938 <input type="text" name="foo"/>
2939 </form>
2940
2941 <p>Selectors can be used in STTS 3 in two different
2942 manners:
2943 <ol>
2944 <li>a selection mechanism equivalent to CSS selection mechanism: declarations
2945 attached to a given selector are applied to elements matching that selector,
2946 <li>fragment descriptions that appear on the right side of declarations.
2947 </li></ol></div>
2948
2949 <h2><a name=Conformance></a>13. Conformance and requirements</h2>
2950
2951 <p>This section defines conformance with the present specification only.
2952
2953 <p>The inability of a user agent to implement part of this specification due to
2954 the limitations of a particular device (e.g., non interactive user agents will
2955 probably not implement dynamic pseudo-classes because they make no sense without
2956 interactivity) does not imply non-conformance.
2957
2958 <p>All specifications reusing Selectors must contain a <a
2959 href="#profiling">Profile</a> listing the
2960 subset of Selectors it accepts or excludes, and describing the constraints
2961 it adds to the current specification.
2962
2963 <p>Invalidity is caused by a parsing error, e.g. an unrecognized token or a toke n
2964 which is not allowed at the current parsing point.
2965
2966 <p>User agents must observe the rules for handling parsing errors:
2967 <ul>
2968 <li>a simple selector containing an undeclared namespace prefix is invalid</li >
2969 <li>a selector containing an invalid simple selector, an invalid combinator
2970 or an invalid token is invalid. </li>
2971 <li>a group of selectors containing an invalid selector is invalid.</li>
2972 </ul>
2973
2974 <p class="foo test10 bar">Specifications reusing Selectors must define how to ha ndle parsing
2975 errors. (In the case of CSS, the entire rule in which the selector is
2976 used is dropped.)</p>
2977
2978 <!-- Apparently all these references are out of date:
2979 <p>Implementations of this specification must behave as
2980 "recipients of text data" as defined by <a href="#refsCWWW">[CWWW]</a>
2981 when parsing selectors and attempting matches. (In particular,
2982 implementations must assume the data is normalized and must not
2983 normalize it.) Normative rules for matching strings are defined in
2984 <a href="#refsCWWW">[CWWW]</a> and <a
2985 href="#refsUNICODE">[UNICODE]</a> and apply to implementations of this
2986 specification.</p>-->
2987
2988 <h2><a name=Tests></a>14. Tests</h2>
2989
2990 <p>This specification has <a
2991 href="http://www.w3.org/Style/CSS/Test/CSS3/Selectors/current/">a test
2992 suite</a> allowing user agents to verify their basic conformance to
2993 the specification. This test suite does not pretend to be exhaustive
2994 and does not cover all possible combined cases of Selectors.</p>
2995
2996 <h2><a name=ACKS></a>15. Acknowledgements</h2>
2997
2998 <p>The CSS working group would like to thank everyone who has sent
2999 comments on this specification over the years.</p>
3000
3001 <p>The working group would like to extend special thanks to Donna
3002 McManus, Justin Baker, Joel Sklar, and Molly Ives Brower who perfermed
3003 the final editorial review.</p>
3004
3005 <h2><a name=references>16. References</a></h2>
3006
3007 <dl class="refs">
3008
3009 <dt>[CSS1]
3010 <dd><a name=refsCSS1></a> Bert Bos, H&aring;kon Wium Lie; "<cite>Cascading Sty le Sheets, level 1</cite>", W3C Recommendation, 17 Dec 1996, revised 11 Jan 1999
3011 <dd>(<code><a href="http://www.w3.org/TR/REC-CSS1">http://www.w3.org/TR/REC-CS S1</a></code>)
3012
3013 <dt>[CSS21]
3014 <dd><a name=refsCSS21></a> Bert Bos, Tantek &Ccedil;elik, Ian Hickson, H&aring ;kon Wium Lie, editors; "<cite>Cascading Style Sheets, level 2 revision 1</cite> ", W3C Working Draft, 13 June 2005
3015 <dd>(<code><a href="http://www.w3.org/TR/CSS21">http://www.w3.org/TR/CSS21</a> </code>)
3016
3017 <dt>[CWWW]
3018 <dd><a name=refsCWWW></a> Martin J. D&uuml;rst, Fran&ccedil;ois Yergeau, Misha Wolf, Asmus Freytag, Tex Texin, editors; "<cite>Character Model for the World W ide Web</cite>", W3C Recommendation, 15 February 2005
3019 <dd>(<code><a href="http://www.w3.org/TR/charmod/">http://www.w3.org/TR/charmo d/</a></code>)
3020
3021 <dt>[FLEX]
3022 <dd><a name="refsFLEX"></a> "<cite>Flex: The Lexical Scanner Generator</cite>" , Version 2.3.7, ISBN 1882114213
3023
3024 <dt>[HTML4]
3025 <dd><a name="refsHTML4"></a> Dave Ragget, Arnaud Le Hors, Ian Jacobs, editors; "<cite>HTML 4.01 Specification</cite>", W3C Recommendation, 24 December 1999
3026 <dd>(<a href="http://www.w3.org/TR/html4/"><code>http://www.w3.org/TR/html4/</ code></a>)
3027
3028 <dt>[MATH]
3029 <dd><a name="refsMATH"></a> Patrick Ion, Robert Miner, editors; "<cite>Mathema tical Markup Language (MathML) 1.01</cite>", W3C Recommendation, revision of 7 J uly 1999
3030 <dd>(<code><a href="http://www.w3.org/TR/REC-MathML/">http://www.w3.org/TR/REC -MathML/</a></code>)
3031
3032 <dt>[RFC3066]
3033 <dd><a name="refsRFC3066"></a> H. Alvestrand; "<cite>Tags for the Identificati on of Languages</cite>", Request for Comments 3066, January 2001
3034 <dd>(<a href="http://www.ietf.org/rfc/rfc3066.txt"><code>http://www.ietf.org/r fc/rfc3066.txt</code></a>)
3035
3036 <dt>[STTS]
3037 <dd><a name=refsSTTS></a> Daniel Glazman; "<cite>Simple Tree Transformation Sh eets 3</cite>", Electricit&eacute; de France, submission to the W3C, 11 November 1998
3038 <dd>(<code><a href="http://www.w3.org/TR/NOTE-STTS3">http://www.w3.org/TR/NOTE -STTS3</a></code>)
3039
3040 <dt>[SVG]
3041 <dd><a name="refsSVG"></a> Jon Ferraiolo, &#34276;&#27810; &#28147;, Dean Jack son, editors; "<cite>Scalable Vector Graphics (SVG) 1.1 Specification</cite>", W 3C Recommendation, 14 January 2003
3042 <dd>(<code><a href="http://www.w3.org/TR/SVG/">http://www.w3.org/TR/SVG/</a></ code>)
3043
3044 <dt>[UNICODE]</dt>
3045 <dd><a name="refsUNICODE"></a> <cite><a
3046 href="http://www.unicode.org/versions/Unicode4.1.0/">The Unicode Standard, Ve rsion 4.1</a></cite>, The Unicode Consortium. Boston, MA, Addison-Wesley, March 2005. ISBN 0-321-18578-1, as amended by <a href="http://www.unicode.org/versions /Unicode4.0.1/">Unicode 4.0.1</a> and <a href="http://www.unicode.org/versions/U nicode4.1.0/">Unicode 4.1.0</a>.
3047 <dd>(<code><a href="http://www.unicode.org/versions/">http://www.unicode.org/v ersions/</a></code>)</dd>
3048
3049 <dt>[XML10]
3050 <dd><a name="refsXML10"></a> Tim Bray, Jean Paoli, C. M. Sperberg-McQueen, Eve Maler, Fran&ccedil;ois Yergeau, editors; "<cite>Extensible Markup Language (XML ) 1.0 (Third Edition)</cite>", W3C Recommendation, 4 February 2004
3051 <dd>(<a href="http://www.w3.org/TR/REC-xml/"><code>http://www.w3.org/TR/REC-xm l/</code></a>)
3052
3053 <dt>[XMLNAMES]
3054 <dd><a name="refsXMLNAMES"></a> Tim Bray, Dave Hollander, Andrew Layman, edito rs; "<cite>Namespaces in XML</cite>", W3C Recommendation, 14 January 1999
3055 <dd>(<a href="http://www.w3.org/TR/REC-xml-names/"><code>http://www.w3.org/TR/ REC-xml-names/</code></a>)
3056
3057 <dt>[YACC]
3058 <dd><a name="refsYACC"></a> S. C. Johnson; "<cite>YACC &mdash; Yet another com piler compiler</cite>", Technical Report, Murray Hill, 1975
3059
3060 </dl>
3061 </body>
3062 </html>
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