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1 <html>
2 <head>
3 <script src="../htmlrunner.js"></script>
4 <script>
5 window.onload = function(){
6 startTest("dom-attr", '');
7
8 // Try to force real results
9 var ret, tmp;
10
11 var elem = document.getElementById("test1");
12 var a = document.getElementsByTagName("a")[0];
13 var num = 10240;
14
15 test( "getAttribute", function(){
16 for ( var i = 0; i < num; i++ )
17 ret = elem.getAttribute("id");
18 });
19
20 test( "element.property", function(){
21 for ( var i = 0; i < num * 2; i++ )
22 ret = elem.id;
23 });
24
25 test( "setAttribute", function(){
26 for ( var i = 0; i < num; i++ )
27 a.setAttribute("id", "foo");
28 });
29
30 test( "element.property = value", function(){
31 for ( var i = 0; i < num; i++ )
32 a.id = "foo";
33 });
34
35 test( "element.expando = value", function(){
36 for ( var i = 0; i < num; i++ )
37 a["test" + num] = function(){};
38 });
39
40 test( "element.expando", function(){
41 for ( var i = 0; i < num; i++ )
42 ret = a["test" + num];
43 });
44
45 endTest();
46 };
47 </script>
48 </head>
49 <body>
50 <div class="head">
51 <p><a href="http://www.w3.org/"><img height=48 alt=W3C src="http://www.w3.org /Icons/w3c_home" width=72></a>
52
53 <h1 id="title">Selectors</h1>
54
55 <h2>W3C Working Draft 15 December 2005</h2>
56
57 <dl>
58
59 <dt>This version:
60
61 <dd><a href="http://www.w3.org/TR/2005/WD-css3-selectors-20051215">
62 http://www.w3.org/TR/2005/WD-css3-selectors-20051215</a>
63
64 <dt>Latest version:
65
66 <dd><a href="http://www.w3.org/TR/css3-selectors">
67 http://www.w3.org/TR/css3-selectors</a>
68
69 <dt>Previous version:
70
71 <dd><a href="http://www.w3.org/TR/2001/CR-css3-selectors-20011113">
72 http://www.w3.org/TR/2001/CR-css3-selectors-20011113</a>
73
74 <dt><a name=editors-list></a>Editors:
75
76 <dd class="vcard"><span class="fn">Daniel Glazman</span> (Invited Expert)</d d>
77
78 <dd class="vcard"><a lang="tr" class="url fn" href="http://www.tantek.com/"> Tantek &Ccedil;elik</a> (Invited Expert)
79
80 <dd class="vcard"><a href="mailto:ian@hixie.ch" class="url fn">Ian Hickson</ a> (<span
81 class="company"><a href="http://www.google.com/">Google</a></span>)
82
83 <dd class="vcard"><span class="fn">Peter Linss</span> (former editor, <span class="company"><a
84 href="http://www.netscape.com/">Netscape/AOL</a></span>)
85
86 <dd class="vcard"><span class="fn">John Williams</span> (former editor, <spa n class="company"><a
87 href="http://www.quark.com/">Quark, Inc.</a></span>)
88
89 </dl>
90
91 <p class="copyright"><a
92 href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">
93 Copyright</a> &copy; 2005 <a href="http://www.w3.org/"><abbr
94 title="World Wide Web Consortium">W3C</abbr></a><sup>&reg;</sup>
95 (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts
96 Institute of Technology">MIT</abbr></a>, <a
97 href="http://www.ercim.org/"><acronym title="European Research
98 Consortium for Informatics and Mathematics">ERCIM</acronym></a>, <a
99 href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C
100 <a
101 href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liabili ty</a>,
102 <a
103 href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark </a>,
104 <a
105 href="http://www.w3.org/Consortium/Legal/copyright-documents">document
106 use</a> rules apply.
107
108 <hr title="Separator for header">
109
110 </div>
111
112 <h2><a name=abstract></a>Abstract</h2>
113
114 <p><em>Selectors</em> are patterns that match against elements in a
115 tree. Selectors have been optimized for use with HTML and XML, and
116 are designed to be usable in performance-critical code.</p>
117
118 <p><acronym title="Cascading Style Sheets">CSS</acronym> (Cascading
119 Style Sheets) is a language for describing the rendering of <acronym
120 title="Hypertext Markup Language">HTML</acronym> and <acronym
121 title="Extensible Markup Language">XML</acronym> documents on
122 screen, on paper, in speech, etc. CSS uses Selectors for binding
123 style properties to elements in the document. This document
124 describes extensions to the selectors defined in CSS level 2. These
125 extended selectors will be used by CSS level 3.
126
127 <p>Selectors define the following function:</p>
128
129 <pre>expression &#x2217; element &rarr; boolean</pre>
130
131 <p>That is, given an element and a selector, this specification
132 defines whether that element matches the selector.</p>
133
134 <p>These expressions can also be used, for instance, to select a set
135 of elements, or a single element from a set of elements, by
136 evaluating the expression across all the elements in a
137 subtree. <acronym title="Simple Tree Transformation
138 Sheets">STTS</acronym> (Simple Tree Transformation Sheets), a
139 language for transforming XML trees, uses this mechanism. <a href="#refsSTTS"> [STTS]</a></p>
140
141 <h2><a name=status></a>Status of this document</h2>
142
143 <p><em>This section describes the status of this document at the
144 time of its publication. Other documents may supersede this
145 document. A list of current W3C publications and the latest revision
146 of this technical report can be found in the <a
147 href="http://www.w3.org/TR/">W3C technical reports index at
148 http://www.w3.org/TR/.</a></em></p>
149
150 <p>This document describes the selectors that already exist in <a
151 href="#refsCSS1"><abbr title="CSS level 1">CSS1</abbr></a> and <a
152 href="#refsCSS21"><abbr title="CSS level 2">CSS2</abbr></a>, and
153 also proposes new selectors for <abbr title="CSS level
154 3">CSS3</abbr> and other languages that may need them.</p>
155
156 <p>The CSS Working Group doesn't expect that all implementations of
157 CSS3 will have to implement all selectors. Instead, there will
158 probably be a small number of variants of CSS3, called profiles. For
159 example, it may be that only a profile for interactive user agents
160 will include all of the selectors.</p>
161
162 <p>This specification is a last call working draft for the the <a
163 href="http://www.w3.org/Style/CSS/members">CSS Working Group</a>
164 (<a href="/Style/">Style Activity</a>). This
165 document is a revision of the <a
166 href="http://www.w3.org/TR/2001/CR-css3-selectors-20011113/">Candidate
167 Recommendation dated 2001 November 13</a>, and has incorporated
168 implementation feedback received in the past few years. It is
169 expected that this last call will proceed straight to Proposed
170 Recommendation stage since it is believed that interoperability will
171 be demonstrable.</p>
172
173 <p>All persons are encouraged to review and implement this
174 specification and return comments to the (<a
175 href="http://lists.w3.org/Archives/Public/www-style/">archived</a>)
176 public mailing list <a
177 href="http://www.w3.org/Mail/Lists.html#www-style">www-style</a>
178 (see <a href="http://www.w3.org/Mail/Request">instructions</a>). W3C
179 Members can also send comments directly to the CSS Working
180 Group.
181 The deadline for comments is 14 January 2006.</p>
182
183 <p>This is still a draft document and may be updated, replaced, or
184 obsoleted by other documents at any time. It is inappropriate to
185 cite a W3C Working Draft as other than &quot;work in progress&quot;.
186
187 <p>This document may be available in <a
188 href="http://www.w3.org/Style/css3-selectors-updates/translations">translation </a>.
189 The English version of this specification is the only normative
190 version.
191
192 <div class="subtoc">
193
194 <h2 id="test1"><a name=contents>Table of contents</a></h2>
195
196 <ul class="toc">
197 <li class="tocline2"><a href="#context">1. Introduction</a>
198 <ul>
199 <li><a href="#dependencies">1.1. Dependencies</a> </li>
200 <li><a href="#terminology">1.2. Terminology</a> </li>
201 <li><a href="#changesFromCSS2">1.3. Changes from CSS2</a> </li>
202 </ul>
203 <li class="tocline2"><a href="#selectors">2. Selectors</a>
204 <li class="tocline2"><a href="#casesens">3. Case sensitivity</a>
205 <li class="tocline2"><a href="#selector-syntax">4. Selector syntax</a>
206 <li class="tocline2"><a href="#grouping">5. Groups of selectors</a>
207 <li class="tocline2"><a href="#simple-selectors">6. Simple selectors</a>
208 <ul class="toc">
209 <li class="tocline3"><a href="#type-selectors">6.1. Type selectors</a>
210 <ul class="toc">
211 <li class="tocline4"><a href="#typenmsp">6.1.1. Type selectors and names paces</a></li>
212 </ul>
213 <li class="tocline3"><a href="#universal-selector">6.2. Universal selector </a>
214 <ul>
215 <li><a href="#univnmsp">6.2.1. Universal selector and namespaces</a></li >
216 </ul>
217 <li class="tocline3"><a href="#attribute-selectors">6.3. Attribute selecto rs</a>
218 <ul class="toc">
219 <li class="tocline4"><a href="#attribute-representation">6.3.1. Represen tation of attributes and attributes values</a>
220 <li><a href="#attribute-substrings">6.3.2. Substring matching attribute selectors</a>
221 <li class="tocline4"><a href="#attrnmsp">6.3.3. Attribute selectors and namespaces</a>
222 <li class="tocline4"><a href="#def-values">6.3.4. Default attribute valu es in DTDs</a></li>
223 </ul>
224 <li class="tocline3"><a href="#class-html">6.4. Class selectors</a>
225 <li class="tocline3"><a href="#id-selectors">6.5. ID selectors</a>
226 <li class="tocline3"><a href="#pseudo-classes">6.6. Pseudo-classes</a>
227 <ul class="toc">
228 <li class="tocline4"><a href="#dynamic-pseudos">6.6.1. Dynamic pseudo-cl asses</a>
229 <li class="tocline4"><a href="#target-pseudo">6.6.2. The :target pseudo- class</a>
230 <li class="tocline4"><a href="#lang-pseudo">6.6.3. The :lang() pseudo-cl ass</a>
231 <li class="tocline4"><a href="#UIstates">6.6.4. UI element states pseudo -classes</a>
232 <li class="tocline4"><a href="#structural-pseudos">6.6.5. Structural pse udo-classes</a>
233 <ul>
234 <li><a href="#root-pseudo">:root pseudo-class</a>
235 <li><a href="#nth-child-pseudo">:nth-child() pseudo-class</a>
236 <li><a href="#nth-last-child-pseudo">:nth-last-child()</a>
237 <li><a href="#nth-of-type-pseudo">:nth-of-type() pseudo-class</a>
238 <li><a href="#nth-last-of-type-pseudo">:nth-last-of-type()</a>
239 <li><a href="#first-child-pseudo">:first-child pseudo-class</a>
240 <li><a href="#last-child-pseudo">:last-child pseudo-class</a>
241 <li><a href="#first-of-type-pseudo">:first-of-type pseudo-class</a>
242 <li><a href="#last-of-type-pseudo">:last-of-type pseudo-class</a>
243 <li><a href="#only-child-pseudo">:only-child pseudo-class</a>
244 <li><a href="#only-of-type-pseudo">:only-of-type pseudo-class</a>
245 <li><a href="#empty-pseudo">:empty pseudo-class</a></li>
246 </ul>
247 <li class="tocline4"><a href="#negation">6.6.7. The negation pseudo-clas s</a></li>
248 </ul>
249 </li>
250 </ul>
251 <li><a href="#pseudo-elements">7. Pseudo-elements</a>
252 <ul>
253 <li><a href="#first-line">7.1. The ::first-line pseudo-element</a>
254 <li><a href="#first-letter">7.2. The ::first-letter pseudo-element</a>
255 <li><a href="#UIfragments">7.3. The ::selection pseudo-element</a>
256 <li><a href="#gen-content">7.4. The ::before and ::after pseudo-elements</ a></li>
257 </ul>
258 <li class="tocline2"><a href="#combinators">8. Combinators</a>
259 <ul class="toc">
260 <li class="tocline3"><a href="#descendant-combinators">8.1. Descendant com binators</a>
261 <li class="tocline3"><a href="#child-combinators">8.2. Child combinators</ a>
262 <li class="tocline3"><a href="#sibling-combinators">8.3. Sibling combinato rs</a>
263 <ul class="toc">
264 <li class="tocline4"><a href="#adjacent-sibling-combinators">8.3.1. Adja cent sibling combinator</a>
265 <li class="tocline4"><a href="#general-sibling-combinators">8.3.2. Gener al sibling combinator</a></li>
266 </ul>
267 </li>
268 </ul>
269 <li class="tocline2"><a href="#specificity">9. Calculating a selector's spec ificity</a>
270 <li class="tocline2"><a href="#w3cselgrammar">10. The grammar of Selectors</ a>
271 <ul class="toc">
272 <li class="tocline3"><a href="#grammar">10.1. Grammar</a>
273 <li class="tocline3"><a href="#lex">10.2. Lexical scanner</a></li>
274 </ul>
275 <li class="tocline2"><a href="#downlevel">11. Namespaces and down-level clie nts</a>
276 <li class="tocline2"><a href="#profiling">12. Profiles</a>
277 <li><a href="#Conformance">13. Conformance and requirements</a>
278 <li><a href="#Tests">14. Tests</a>
279 <li><a href="#ACKS">15. Acknowledgements</a>
280 <li class="tocline2"><a href="#references">16. References</a>
281 </ul>
282
283 </div>
284
285 <h2><a name=context>1. Introduction</a></h2>
286
287 <h3><a name=dependencies></a>1.1. Dependencies</h3>
288
289 <p>Some features of this specification are specific to CSS, or have
290 particular limitations or rules specific to CSS. In this
291 specification, these have been described in terms of CSS2.1. <a
292 href="#refsCSS21">[CSS21]</a></p>
293
294 <h3><a name=terminology></a>1.2. Terminology</h3>
295
296 <p>All of the text of this specification is normative except
297 examples, notes, and sections explicitly marked as
298 non-normative.</p>
299
300 <h3><a name=changesFromCSS2></a>1.3. Changes from CSS2</h3>
301
302 <p><em>This section is non-normative.</em></p>
303
304 <p>The main differences between the selectors in CSS2 and those in
305 Selectors are:
306
307 <ul>
308
309 <li>the list of basic definitions (selector, group of selectors,
310 simple selector, etc.) has been changed; in particular, what was
311 referred to in CSS2 as a simple selector is now called a sequence
312 of simple selectors, and the term "simple selector" is now used for
313 the components of this sequence</li>
314
315 <li>an optional namespace component is now allowed in type element
316 selectors, the universal selector and attribute selectors</li>
317
318 <li>a <a href="#general-sibling-combinators">new combinator</a> has been intr oduced</li>
319
320 <li>new simple selectors including substring matching attribute
321 selectors, and new pseudo-classes</li>
322
323 <li>new pseudo-elements, and introduction of the "::" convention
324 for pseudo-elements</li>
325
326 <li>the grammar has been rewritten</li>
327
328 <li>profiles to be added to specifications integrating Selectors
329 and defining the set of selectors which is actually supported by
330 each specification</li>
331
332 <li>Selectors are now a CSS3 Module and an independent
333 specification; other specifications can now refer to this document
334 independently of CSS</li>
335
336 <li>the specification now has its own test suite</li>
337
338 </ul>
339
340 <h2><a name=selectors></a>2. Selectors</h2>
341
342 <p><em>This section is non-normative, as it merely summarizes the
343 following sections.</em></p>
344
345 <p>A Selector represents a structure. This structure can be used as a
346 condition (e.g. in a CSS rule) that determines which elements a
347 selector matches in the document tree, or as a flat description of the
348 HTML or XML fragment corresponding to that structure.</p>
349
350 <p>Selectors may range from simple element names to rich contextual
351 representations.</p>
352
353 <p>The following table summarizes the Selector syntax:</p>
354
355 <table class="selectorsReview">
356 <thead>
357 <tr>
358 <th class="pattern">Pattern</th>
359 <th class="meaning">Meaning</th>
360 <th class="described">Described in section</th>
361 <th class="origin">First defined in CSS level</th></tr>
362 <tbody>
363 <tr>
364 <td class="pattern">*</td>
365 <td class="meaning">any element</td>
366 <td class="described"><a
367 href="#universal-selector">Universal
368 selector</a></td>
369 <td class="origin">2</td></tr>
370 <tr>
371 <td class="pattern">E</td>
372 <td class="meaning">an element of type E</td>
373 <td class="described"><a
374 href="#type-selectors">Type selector</a></td>
375 <td class="origin">1</td></tr>
376 <tr>
377 <td class="pattern">E[foo]</td>
378 <td class="meaning">an E element with a "foo" attribute</td>
379 <td class="described"><a
380 href="#attribute-selectors">Attribute
381 selectors</a></td>
382 <td class="origin">2</td></tr>
383 <tr>
384 <td class="pattern">E[foo="bar"]</td>
385 <td class="meaning">an E element whose "foo" attribute value is exactly
386 equal to "bar"</td>
387 <td class="described"><a
388 href="#attribute-selectors">Attribute
389 selectors</a></td>
390 <td class="origin">2</td></tr>
391 <tr>
392 <td class="pattern">E[foo~="bar"]</td>
393 <td class="meaning">an E element whose "foo" attribute value is a list of
394 space-separated values, one of which is exactly equal to "bar"</td>
395 <td class="described"><a
396 href="#attribute-selectors">Attribute
397 selectors</a></td>
398 <td class="origin">2</td></tr>
399 <tr>
400 <td class="pattern">E[foo^="bar"]</td>
401 <td class="meaning">an E element whose "foo" attribute value begins exactly
402 with the string "bar"</td>
403 <td class="described"><a
404 href="#attribute-selectors">Attribute
405 selectors</a></td>
406 <td class="origin">3</td></tr>
407 <tr>
408 <td class="pattern">E[foo$="bar"]</td>
409 <td class="meaning">an E element whose "foo" attribute value ends exactly
410 with the string "bar"</td>
411 <td class="described"><a
412 href="#attribute-selectors">Attribute
413 selectors</a></td>
414 <td class="origin">3</td></tr>
415 <tr>
416 <td class="pattern">E[foo*="bar"]</td>
417 <td class="meaning">an E element whose "foo" attribute value contains the
418 substring "bar"</td>
419 <td class="described"><a
420 href="#attribute-selectors">Attribute
421 selectors</a></td>
422 <td class="origin">3</td></tr>
423 <tr>
424 <td class="pattern">E[hreflang|="en"]</td>
425 <td class="meaning">an E element whose "hreflang" attribute has a hyphen-sep arated
426 list of values beginning (from the left) with "en"</td>
427 <td class="described"><a
428 href="#attribute-selectors">Attribute
429 selectors</a></td>
430 <td class="origin">2</td></tr>
431 <tr>
432 <td class="pattern">E:root</td>
433 <td class="meaning">an E element, root of the document</td>
434 <td class="described"><a
435 href="#structural-pseudos">Structural
436 pseudo-classes</a></td>
437 <td class="origin">3</td></tr>
438 <tr>
439 <td class="pattern">E:nth-child(n)</td>
440 <td class="meaning">an E element, the n-th child of its parent</td>
441 <td class="described"><a
442 href="#structural-pseudos">Structural
443 pseudo-classes</a></td>
444 <td class="origin">3</td></tr>
445 <tr>
446 <td class="pattern">E:nth-last-child(n)</td>
447 <td class="meaning">an E element, the n-th child of its parent, counting
448 from the last one</td>
449 <td class="described"><a
450 href="#structural-pseudos">Structural
451 pseudo-classes</a></td>
452 <td class="origin">3</td></tr>
453 <tr>
454 <td class="pattern">E:nth-of-type(n)</td>
455 <td class="meaning">an E element, the n-th sibling of its type</td>
456 <td class="described"><a
457 href="#structural-pseudos">Structural
458 pseudo-classes</a></td>
459 <td class="origin">3</td></tr>
460 <tr>
461 <td class="pattern">E:nth-last-of-type(n)</td>
462 <td class="meaning">an E element, the n-th sibling of its type, counting
463 from the last one</td>
464 <td class="described"><a
465 href="#structural-pseudos">Structural
466 pseudo-classes</a></td>
467 <td class="origin">3</td></tr>
468 <tr>
469 <td class="pattern">E:first-child</td>
470 <td class="meaning">an E element, first child of its parent</td>
471 <td class="described"><a
472 href="#structural-pseudos">Structural
473 pseudo-classes</a></td>
474 <td class="origin">2</td></tr>
475 <tr>
476 <td class="pattern">E:last-child</td>
477 <td class="meaning">an E element, last child of its parent</td>
478 <td class="described"><a
479 href="#structural-pseudos">Structural
480 pseudo-classes</a></td>
481 <td class="origin">3</td></tr>
482 <tr>
483 <td class="pattern">E:first-of-type</td>
484 <td class="meaning">an E element, first sibling of its type</td>
485 <td class="described"><a
486 href="#structural-pseudos">Structural
487 pseudo-classes</a></td>
488 <td class="origin">3</td></tr>
489 <tr>
490 <td class="pattern">E:last-of-type</td>
491 <td class="meaning">an E element, last sibling of its type</td>
492 <td class="described"><a
493 href="#structural-pseudos">Structural
494 pseudo-classes</a></td>
495 <td class="origin">3</td></tr>
496 <tr>
497 <td class="pattern">E:only-child</td>
498 <td class="meaning">an E element, only child of its parent</td>
499 <td class="described"><a
500 href="#structural-pseudos">Structural
501 pseudo-classes</a></td>
502 <td class="origin">3</td></tr>
503 <tr>
504 <td class="pattern">E:only-of-type</td>
505 <td class="meaning">an E element, only sibling of its type</td>
506 <td class="described"><a
507 href="#structural-pseudos">Structural
508 pseudo-classes</a></td>
509 <td class="origin">3</td></tr>
510 <tr>
511 <td class="pattern">E:empty</td>
512 <td class="meaning">an E element that has no children (including text
513 nodes)</td>
514 <td class="described"><a
515 href="#structural-pseudos">Structural
516 pseudo-classes</a></td>
517 <td class="origin">3</td></tr>
518 <tr>
519 <td class="pattern">E:link<br>E:visited</td>
520 <td class="meaning">an E element being the source anchor of a hyperlink of
521 which the target is not yet visited (:link) or already visited
522 (:visited)</td>
523 <td class="described"><a
524 href="#link">The link
525 pseudo-classes</a></td>
526 <td class="origin">1</td></tr>
527 <tr>
528 <td class="pattern">E:active<br>E:hover<br>E:focus</td>
529 <td class="meaning">an E element during certain user actions</td>
530 <td class="described"><a
531 href="#useraction-pseudos">The user
532 action pseudo-classes</a></td>
533 <td class="origin">1 and 2</td></tr>
534 <tr>
535 <td class="pattern">E:target</td>
536 <td class="meaning">an E element being the target of the referring URI</td>
537 <td class="described"><a
538 href="#target-pseudo">The target
539 pseudo-class</a></td>
540 <td class="origin">3</td></tr>
541 <tr>
542 <td class="pattern">E:lang(fr)</td>
543 <td class="meaning">an element of type E in language "fr" (the document
544 language specifies how language is determined)</td>
545 <td class="described"><a
546 href="#lang-pseudo">The :lang()
547 pseudo-class</a></td>
548 <td class="origin">2</td></tr>
549 <tr>
550 <td class="pattern">E:enabled<br>E:disabled</td>
551 <td class="meaning">a user interface element E which is enabled or
552 disabled</td>
553 <td class="described"><a
554 href="#UIstates">The UI element states
555 pseudo-classes</a></td>
556 <td class="origin">3</td></tr>
557 <tr>
558 <td class="pattern">E:checked<!--<br>E:indeterminate--></td>
559 <td class="meaning">a user interface element E which is checked<!-- or in an
560 indeterminate state--> (for instance a radio-button or checkbox)</td>
561 <td class="described"><a
562 href="#UIstates">The UI element states
563 pseudo-classes</a></td>
564 <td class="origin">3</td></tr>
565 <tr>
566 <td class="pattern">E::first-line</td>
567 <td class="meaning">the first formatted line of an E element</td>
568 <td class="described"><a
569 href="#first-line">The ::first-line
570 pseudo-element</a></td>
571 <td class="origin">1</td></tr>
572 <tr>
573 <td class="pattern">E::first-letter</td>
574 <td class="meaning">the first formatted letter of an E element</td>
575 <td class="described"><a
576 href="#first-letter">The ::first-letter
577 pseudo-element</a></td>
578 <td class="origin">1</td></tr>
579 <tr>
580 <td class="pattern">E::selection</td>
581 <td class="meaning">the portion of an E element that is currently
582 selected/highlighted by the user</td>
583 <td class="described"><a
584 href="#UIfragments">The UI element
585 fragments pseudo-elements</a></td>
586 <td class="origin">3</td></tr>
587 <tr>
588 <td class="pattern">E::before</td>
589 <td class="meaning">generated content before an E element</td>
590 <td class="described"><a
591 href="#gen-content">The ::before
592 pseudo-element</a></td>
593 <td class="origin">2</td></tr>
594 <tr>
595 <td class="pattern">E::after</td>
596 <td class="meaning">generated content after an E element</td>
597 <td class="described"><a
598 href="#gen-content">The ::after
599 pseudo-element</a></td>
600 <td class="origin">2</td></tr>
601 <tr>
602 <td class="pattern">E.warning</td>
603 <td class="meaning">an E element whose class is
604 "warning" (the document language specifies how class is determined).</td>
605 <td class="described"><a
606 href="#class-html">Class
607 selectors</a></td>
608 <td class="origin">1</td></tr>
609 <tr>
610 <td class="pattern">E#myid</td>
611 <td class="meaning">an E element with ID equal to "myid".</td>
612 <td class="described"><a
613 href="#id-selectors">ID
614 selectors</a></td>
615 <td class="origin">1</td></tr>
616 <tr>
617 <td class="pattern">E:not(s)</td>
618 <td class="meaning">an E element that does not match simple selector s</td>
619 <td class="described"><a
620 href="#negation">Negation
621 pseudo-class</a></td>
622 <td class="origin">3</td></tr>
623 <tr>
624 <td class="pattern">E F</td>
625 <td class="meaning">an F element descendant of an E element</td>
626 <td class="described"><a
627 href="#descendant-combinators">Descendant
628 combinator</a></td>
629 <td class="origin">1</td></tr>
630 <tr>
631 <td class="pattern">E &gt; F</td>
632 <td class="meaning">an F element child of an E element</td>
633 <td class="described"><a
634 href="#child-combinators">Child
635 combinator</a></td>
636 <td class="origin">2</td></tr>
637 <tr>
638 <td class="pattern">E + F</td>
639 <td class="meaning">an F element immediately preceded by an E element</td>
640 <td class="described"><a
641 href="#adjacent-sibling-combinators">Adjacent sibling combinator</a></td>
642 <td class="origin">2</td></tr>
643 <tr>
644 <td class="pattern">E ~ F</td>
645 <td class="meaning">an F element preceded by an E element</td>
646 <td class="described"><a
647 href="#general-sibling-combinators">General sibling combinator</a></td>
648 <td class="origin">3</td></tr></tbody></table>
649
650 <p>The meaning of each selector is derived from the table above by
651 prepending "matches" to the contents of each cell in the "Meaning"
652 column.</p>
653
654 <h2><a name=casesens>3. Case sensitivity</a></h2>
655
656 <p>The case sensitivity of document language element names, attribute
657 names, and attribute values in selectors depends on the document
658 language. For example, in HTML, element names are case-insensitive,
659 but in XML, they are case-sensitive.</p>
660
661 <h2><a name=selector-syntax>4. Selector syntax</a></h2>
662
663 <p>A <dfn><a name=selector>selector</a></dfn> is a chain of one
664 or more <a href="#sequence">sequences of simple selectors</a>
665 separated by <a href="#combinators">combinators</a>.</p>
666
667 <p>A <dfn><a name=sequence>sequence of simple selectors</a></dfn>
668 is a chain of <a href="#simple-selectors-dfn">simple selectors</a>
669 that are not separated by a <a href="#combinators">combinator</a>. It
670 always begins with a <a href="#type-selectors">type selector</a> or a
671 <a href="#universal-selector">universal selector</a>. No other type
672 selector or universal selector is allowed in the sequence.</p>
673
674 <p>A <dfn><a name=simple-selectors-dfn></a><a
675 href="#simple-selectors">simple selector</a></dfn> is either a <a
676 href="#type-selectors">type selector</a>, <a
677 href="#universal-selector">universal selector</a>, <a
678 href="#attribute-selectors">attribute selector</a>, <a
679 href="#class-html">class selector</a>, <a
680 href="#id-selectors">ID selector</a>, <a
681 href="#content-selectors">content selector</a>, or <a
682 href="#pseudo-classes">pseudo-class</a>. One <a
683 href="#pseudo-elements">pseudo-element</a> may be appended to the last
684 sequence of simple selectors.</p>
685
686 <p><dfn>Combinators</dfn> are: white space, &quot;greater-than
687 sign&quot; (U+003E, <code>&gt;</code>), &quot;plus sign&quot; (U+002B,
688 <code>+</code>) and &quot;tilde&quot; (U+007E, <code>~</code>). White
689 space may appear between a combinator and the simple selectors around
690 it. <a name=whitespace></a>Only the characters "space" (U+0020), "tab"
691 (U+0009), "line feed" (U+000A), "carriage return" (U+000D), and "form
692 feed" (U+000C) can occur in white space. Other space-like characters,
693 such as "em-space" (U+2003) and "ideographic space" (U+3000), are
694 never part of white space.</p>
695
696 <p>The elements of a document tree that are represented by a selector
697 are the <dfn><a name=subject></a>subjects of the selector</dfn>. A
698 selector consisting of a single sequence of simple selectors
699 represents any element satisfying its requirements. Prepending another
700 sequence of simple selectors and a combinator to a sequence imposes
701 additional matching constraints, so the subjects of a selector are
702 always a subset of the elements represented by the last sequence of
703 simple selectors.</p>
704
705 <p>An empty selector, containing no sequence of simple selectors and
706 no pseudo-element, is an <a href="#Conformance">invalid
707 selector</a>.</p>
708
709 <h2><a name=grouping>5. Groups of selectors</a></h2>
710
711 <p>When several selectors share the same declarations, they may be
712 grouped into a comma-separated list. (A comma is U+002C.)</p>
713
714 <div class="example">
715 <p>CSS examples:</p>
716 <p>In this example, we condense three rules with identical
717 declarations into one. Thus,</p>
718 <pre>h1 { font-family: sans-serif }
719 h2 { font-family: sans-serif }
720 h3 { font-family: sans-serif }</pre>
721 <p>is equivalent to:</p>
722 <pre>h1, h2, h3 { font-family: sans-serif }</pre>
723 </div>
724
725 <p><strong>Warning</strong>: the equivalence is true in this example
726 because all the selectors are valid selectors. If just one of these
727 selectors were invalid, the entire group of selectors would be
728 invalid. This would invalidate the rule for all three heading
729 elements, whereas in the former case only one of the three individual
730 heading rules would be invalidated.</p>
731
732
733 <h2><a name=simple-selectors>6. Simple selectors</a></h2>
734
735 <h3><a name=type-selectors>6.1. Type selector</a></h3>
736
737 <p>A <dfn>type selector</dfn> is the name of a document language
738 element type. A type selector represents an instance of the element
739 type in the document tree.</p>
740
741 <div class="example">
742 <p>Example:</p>
743 <p>The following selector represents an <code>h1</code> element in the document tree:</p>
744 <pre>h1</pre>
745 </div>
746
747
748 <h4><a name=typenmsp>6.1.1. Type selectors and namespaces</a></h4>
749
750 <p>Type selectors allow an optional namespace (<a
751 href="#refsXMLNAMES">[XMLNAMES]</a>) component. A namespace prefix
752 that has been previously declared may be prepended to the element name
753 separated by the namespace separator &quot;vertical bar&quot;
754 (U+007C, <code>|</code>).</p>
755
756 <p>The namespace component may be left empty to indicate that the
757 selector is only to represent elements with no declared namespace.</p>
758
759 <p>An asterisk may be used for the namespace prefix, indicating that
760 the selector represents elements in any namespace (including elements
761 with no namespace).</p>
762
763 <p>Element type selectors that have no namespace component (no
764 namespace separator), represent elements without regard to the
765 element's namespace (equivalent to "<code>*|</code>") unless a default
766 namespace has been declared. If a default namespace has been declared,
767 the selector will represent only elements in the default
768 namespace.</p>
769
770 <p>A type selector containing a namespace prefix that has not been
771 previously declared is an <a href="#Conformance">invalid</a> selector.
772 The mechanism for declaring a namespace prefix is left up to the
773 language implementing Selectors. In CSS, such a mechanism is defined
774 in the General Syntax module.</p>
775
776 <p>In a namespace-aware client, element type selectors will only match
777 against the <a
778 href="http://www.w3.org/TR/REC-xml-names/#NT-LocalPart">local part</a>
779 of the element's <a
780 href="http://www.w3.org/TR/REC-xml-names/#ns-qualnames">qualified
781 name</a>. See <a href="#downlevel">below</a> for notes about matching
782 behaviors in down-level clients.</p>
783
784 <p>In summary:</p>
785
786 <dl>
787 <dt><code>ns|E</code></dt>
788 <dd>elements with name E in namespace ns</dd>
789 <dt><code>*|E</code></dt>
790 <dd>elements with name E in any namespace, including those without any
791 declared namespace</dd>
792 <dt><code>|E</code></dt>
793 <dd>elements with name E without any declared namespace</dd>
794 <dt><code>E</code></dt>
795 <dd>if no default namespace has been specified, this is equivalent to *|E.
796 Otherwise it is equivalent to ns|E where ns is the default namespace.</dd>
797 </dl>
798
799 <div class="example">
800 <p>CSS examples:</p>
801
802 <pre>@namespace foo url(http://www.example.com);
803 foo|h1 { color: blue }
804 foo|* { color: yellow }
805 |h1 { color: red }
806 *|h1 { color: green }
807 h1 { color: green }</pre>
808
809 <p>The first rule will match only <code>h1</code> elements in the
810 "http://www.example.com" namespace.</p>
811
812 <p>The second rule will match all elements in the
813 "http://www.example.com" namespace.</p>
814
815 <p>The third rule will match only <code>h1</code> elements without
816 any declared namespace.</p>
817
818 <p>The fourth rule will match <code>h1</code> elements in any
819 namespace (including those without any declared namespace).</p>
820
821 <p>The last rule is equivalent to the fourth rule because no default
822 namespace has been defined.</p>
823
824 </div>
825
826 <h3><a name=universal-selector>6.2. Universal selector</a> </h3>
827
828 <p>The <dfn>universal selector</dfn>, written &quot;asterisk&quot;
829 (<code>*</code>), represents the qualified name of any element
830 type. It represents any single element in the document tree in any
831 namespace (including those without any declared namespace) if no
832 default namespace has been specified. If a default namespace has been
833 specified, see <a href="#univnmsp">Universal selector and
834 Namespaces</a> below.</p>
835
836 <p>If the universal selector is not the only component of a sequence
837 of simple selectors, the <code>*</code> may be omitted.</p>
838
839 <div class="example">
840 <p>Examples:</p>
841 <ul>
842 <li><code>*[hreflang|=en]</code> and <code>[hreflang|=en]</code> are equivalen t,</li>
843 <li><code>*.warning</code> and <code>.warning</code> are equivalent,</li>
844 <li><code>*#myid</code> and <code>#myid</code> are equivalent.</li>
845 </ul>
846 </div>
847
848 <p class="note"><strong>Note:</strong> it is recommended that the
849 <code>*</code>, representing the universal selector, not be
850 omitted.</p>
851
852 <h4><a name=univnmsp>6.2.1. Universal selector and namespaces</a></h4>
853
854 <p>The universal selector allows an optional namespace component. It
855 is used as follows:</p>
856
857 <dl>
858 <dt><code>ns|*</code></dt>
859 <dd>all elements in namespace ns</dd>
860 <dt><code>*|*</code></dt>
861 <dd>all elements</dd>
862 <dt><code>|*</code></dt>
863 <dd>all elements without any declared namespace</dd>
864 <dt><code>*</code></dt>
865 <dd>if no default namespace has been specified, this is equivalent to *|*.
866 Otherwise it is equivalent to ns|* where ns is the default namespace.</dd>
867 </dl>
868
869 <p>A universal selector containing a namespace prefix that has not
870 been previously declared is an <a href="#Conformance">invalid</a>
871 selector. The mechanism for declaring a namespace prefix is left up
872 to the language implementing Selectors. In CSS, such a mechanism is
873 defined in the General Syntax module.</p>
874
875
876 <h3><a name=attribute-selectors>6.3. Attribute selectors</a></h3>
877
878 <p>Selectors allow the representation of an element's attributes. When
879 a selector is used as an expression to match against an element,
880 attribute selectors must be considered to match an element if that
881 element has an attribute that matches the attribute represented by the
882 attribute selector.</p>
883
884 <h4><a name=attribute-representation>6.3.1. Attribute presence and values
885 selectors</a></h4>
886
887 <p>CSS2 introduced four attribute selectors:</p>
888
889 <dl>
890 <dt><code>[att]</code>
891 <dd>Represents an element with the <code>att</code> attribute, whatever the va lue of
892 the attribute.</dd>
893 <dt><code>[att=val]</code></dt>
894 <dd>Represents an element with the <code>att</code> attribute whose value is e xactly
895 "val".</dd>
896 <dt><code>[att~=val]</code></dt>
897 <dd>Represents an element with the <code>att</code> attribute whose value is a <a
898 href="#whitespace">whitespace</a>-separated list of words, one of
899 which is exactly "val". If "val" contains whitespace, it will never
900 represent anything (since the words are <em>separated</em> by
901 spaces).</dd>
902 <dt><code>[att|=val]</code>
903 <dd>Represents an element with the <code>att</code> attribute, its value eithe r
904 being exactly "val" or beginning with "val" immediately followed by
905 "-" (U+002D). This is primarily intended to allow language subcode
906 matches (e.g., the <code>hreflang</code> attribute on the
907 <code>link</code> element in HTML) as described in RFC 3066 (<a
908 href="#refsRFC3066">[RFC3066]</a>). For <code>lang</code> (or
909 <code>xml:lang</code>) language subcode matching, please see <a
910 href="#lang-pseudo">the <code>:lang</code> pseudo-class</a>.</dd>
911 </dl>
912
913 <p>Attribute values must be identifiers or strings. The
914 case-sensitivity of attribute names and values in selectors depends on
915 the document language.</p>
916
917 <div class="example">
918
919 <p>Examples:</p>
920
921 <p>The following attribute selector represents an <code>h1</code>
922 element that carries the <code>title</code> attribute, whatever its
923 value:</p>
924
925 <pre>h1[title]</pre>
926
927 <p>In the following example, the selector represents a
928 <code>span</code> element whose <code>class</code> attribute has
929 exactly the value "example":</p>
930
931 <pre>span[class="example"]</pre>
932
933 <p>Multiple attribute selectors can be used to represent several
934 attributes of an element, or several conditions on the same
935 attribute. Here, the selector represents a <code>span</code> element
936 whose <code>hello</code> attribute has exactly the value "Cleveland"
937 and whose <code>goodbye</code> attribute has exactly the value
938 "Columbus":</p>
939
940 <pre>span[hello="Cleveland"][goodbye="Columbus"]</pre>
941
942 <p>The following selectors illustrate the differences between "="
943 and "~=". The first selector will represent, for example, the value
944 "copyright copyleft copyeditor" on a <code>rel</code> attribute. The
945 second selector will only represent an <code>a</code> element with
946 an <code>href</code> attribute having the exact value
947 "http://www.w3.org/".</p>
948
949 <pre>a[rel~="copyright"]
950 a[href="http://www.w3.org/"]</pre>
951
952 <p>The following selector represents a <code>link</code> element
953 whose <code>hreflang</code> attribute is exactly "fr".</p>
954
955 <pre>link[hreflang=fr]</pre>
956
957 <p>The following selector represents a <code>link</code> element for
958 which the values of the <code>hreflang</code> attribute begins with
959 "en", including "en", "en-US", and "en-cockney":</p>
960
961 <pre>link[hreflang|="en"]</pre>
962
963 <p>Similarly, the following selectors represents a
964 <code>DIALOGUE</code> element whenever it has one of two different
965 values for an attribute <code>character</code>:</p>
966
967 <pre>DIALOGUE[character=romeo]
968 DIALOGUE[character=juliet]</pre>
969
970 </div>
971
972 <h4><a name=attribute-substrings></a>6.3.2. Substring matching attribute
973 selectors</h4>
974
975 <p>Three additional attribute selectors are provided for matching
976 substrings in the value of an attribute:</p>
977
978 <dl>
979 <dt><code>[att^=val]</code></dt>
980 <dd>Represents an element with the <code>att</code> attribute whose value begi ns
981 with the prefix "val".</dd>
982 <dt><code>[att$=val]</code>
983 <dd>Represents an element with the <code>att</code> attribute whose value ends with
984 the suffix "val".</dd>
985 <dt><code>[att*=val]</code>
986 <dd>Represents an element with the <code>att</code> attribute whose value cont ains
987 at least one instance of the substring "val".</dd>
988 </dl>
989
990 <p>Attribute values must be identifiers or strings. The
991 case-sensitivity of attribute names in selectors depends on the
992 document language.</p>
993
994 <div class="example">
995 <p>Examples:</p>
996 <p>The following selector represents an HTML <code>object</code>, referencing a n
997 image:</p>
998 <pre>object[type^="image/"]</pre>
999 <p>The following selector represents an HTML anchor <code>a</code> with an
1000 <code>href</code> attribute whose value ends with ".html".</p>
1001 <pre>a[href$=".html"]</pre>
1002 <p>The following selector represents an HTML paragraph with a <code>title</code >
1003 attribute whose value contains the substring "hello"</p>
1004 <pre>p[title*="hello"]</pre>
1005 </div>
1006
1007 <h4><a name=attrnmsp>6.3.3. Attribute selectors and namespaces</a></h4>
1008
1009 <p>Attribute selectors allow an optional namespace component to the
1010 attribute name. A namespace prefix that has been previously declared
1011 may be prepended to the attribute name separated by the namespace
1012 separator &quot;vertical bar&quot; (<code>|</code>). In keeping with
1013 the Namespaces in the XML recommendation, default namespaces do not
1014 apply to attributes, therefore attribute selectors without a namespace
1015 component apply only to attributes that have no declared namespace
1016 (equivalent to "<code>|attr</code>"). An asterisk may be used for the
1017 namespace prefix indicating that the selector is to match all
1018 attribute names without regard to the attribute's namespace.
1019
1020 <p>An attribute selector with an attribute name containing a namespace
1021 prefix that has not been previously declared is an <a
1022 href="#Conformance">invalid</a> selector. The mechanism for declaring
1023 a namespace prefix is left up to the language implementing Selectors.
1024 In CSS, such a mechanism is defined in the General Syntax module.
1025
1026 <div class="example">
1027 <p>CSS examples:</p>
1028 <pre>@namespace foo "http://www.example.com";
1029 [foo|att=val] { color: blue }
1030 [*|att] { color: yellow }
1031 [|att] { color: green }
1032 [att] { color: green }</pre>
1033
1034 <p>The first rule will match only elements with the attribute
1035 <code>att</code> in the "http://www.example.com" namespace with the
1036 value "val".</p>
1037
1038 <p>The second rule will match only elements with the attribute
1039 <code>att</code> regardless of the namespace of the attribute
1040 (including no declared namespace).</p>
1041
1042 <p>The last two rules are equivalent and will match only elements
1043 with the attribute <code>att</code> where the attribute is not
1044 declared to be in a namespace.</p>
1045
1046 </div>
1047
1048 <h4><a name=def-values>6.3.4. Default attribute values in DTDs</a></h4>
1049
1050 <p>Attribute selectors represent explicitly set attribute values in
1051 the document tree. Default attribute values may be defined in a DTD or
1052 elsewhere, but cannot always be selected by attribute
1053 selectors. Selectors should be designed so that they work even if the
1054 default values are not included in the document tree.</p>
1055
1056 <p>More precisely, a UA is <em>not</em> required to read an "external
1057 subset" of the DTD but <em>is</em> required to look for default
1058 attribute values in the document's "internal subset." (See <a
1059 href="#refsXML10">[XML10]</a> for definitions of these subsets.)</p>
1060
1061 <p>A UA that recognizes an XML namespace <a
1062 href="#refsXMLNAMES">[XMLNAMES]</a> is not required to use its
1063 knowledge of that namespace to treat default attribute values as if
1064 they were present in the document. (For example, an XHTML UA is not
1065 required to use its built-in knowledge of the XHTML DTD.)</p>
1066
1067 <p class="note"><strong>Note:</strong> Typically, implementations
1068 choose to ignore external subsets.</p>
1069
1070 <div class="example">
1071 <p>Example:</p>
1072
1073 <p>Consider an element EXAMPLE with an attribute "notation" that has a
1074 default value of "decimal". The DTD fragment might be</p>
1075
1076 <pre class="dtd-example">&lt;!ATTLIST EXAMPLE notation (decimal,octal) "decimal" ></pre>
1077
1078 <p>If the style sheet contains the rules</p>
1079
1080 <pre>EXAMPLE[notation=decimal] { /*... default property settings ...*/ }
1081 EXAMPLE[notation=octal] { /*... other settings...*/ }</pre>
1082
1083 <p>the first rule will not match elements whose "notation" attribute
1084 is set by default, i.e. not set explicitly. To catch all cases, the
1085 attribute selector for the default value must be dropped:</p>
1086
1087 <pre>EXAMPLE { /*... default property settings ...*/ }
1088 EXAMPLE[notation=octal] { /*... other settings...*/ }</pre>
1089
1090 <p>Here, because the selector <code>EXAMPLE[notation=octal]</code> is
1091 more specific than the tag
1092 selector alone, the style declarations in the second rule will override
1093 those in the first for elements that have a "notation" attribute value
1094 of "octal". Care has to be taken that all property declarations that
1095 are to apply only to the default case are overridden in the non-default
1096 cases' style rules.</p>
1097
1098 </div>
1099
1100 <h3><a name=class-html>6.4. Class selectors</a></h3>
1101
1102 <p>Working with HTML, authors may use the period (U+002E,
1103 <code>.</code>) notation as an alternative to the <code>~=</code>
1104 notation when representing the <code>class</code> attribute. Thus, for
1105 HTML, <code>div.value</code> and <code>div[class~=value]</code> have
1106 the same meaning. The attribute value must immediately follow the
1107 &quot;period&quot; (<code>.</code>).</p>
1108
1109 <p>UAs may apply selectors using the period (.) notation in XML
1110 documents if the UA has namespace-specific knowledge that allows it to
1111 determine which attribute is the &quot;class&quot; attribute for the
1112 respective namespace. One such example of namespace-specific knowledge
1113 is the prose in the specification for a particular namespace (e.g. SVG
1114 1.0 <a href="#refsSVG">[SVG]</a> describes the <a
1115 href="http://www.w3.org/TR/2001/PR-SVG-20010719/styling.html#ClassAttribute">SVG
1116 &quot;class&quot; attribute</a> and how a UA should interpret it, and
1117 similarly MathML 1.01 <a href="#refsMATH">[MATH]</a> describes the <a
1118 href="http://www.w3.org/1999/07/REC-MathML-19990707/chapter2.html#sec2.3.4">Math ML
1119 &quot;class&quot; attribute</a>.)</p>
1120
1121 <div class="example">
1122 <p>CSS examples:</p>
1123
1124 <p>We can assign style information to all elements with
1125 <code>class~="pastoral"</code> as follows:</p>
1126
1127 <pre>*.pastoral { color: green } /* all elements with class~=pastoral */</pre >
1128
1129 <p>or just</p>
1130
1131 <pre>.pastoral { color: green } /* all elements with class~=pastoral */</pre>
1132
1133 <p>The following assigns style only to H1 elements with
1134 <code>class~="pastoral"</code>:</p>
1135
1136 <pre>H1.pastoral { color: green } /* H1 elements with class~=pastoral */</pre >
1137
1138 <p>Given these rules, the first H1 instance below would not have
1139 green text, while the second would:</p>
1140
1141 <pre>&lt;H1&gt;Not green&lt;/H1&gt;
1142 &lt;H1 class="pastoral"&gt;Very green&lt;/H1&gt;</pre>
1143
1144 </div>
1145
1146 <p>To represent a subset of "class" values, each value must be preceded
1147 by a ".", in any order.</P>
1148
1149 <div class="example">
1150
1151 <p>CSS example:</p>
1152
1153 <p>The following rule matches any P element whose "class" attribute
1154 has been assigned a list of <a
1155 href="#whitespace">whitespace</a>-separated values that includes
1156 "pastoral" and "marine":</p>
1157
1158 <pre>p.pastoral.marine { color: green }</pre>
1159
1160 <p>This rule matches when <code>class="pastoral blue aqua
1161 marine"</code> but does not match for <code>class="pastoral
1162 blue"</code>.</p>
1163
1164 </div>
1165
1166 <p class="note"><strong>Note:</strong> Because CSS gives considerable
1167 power to the "class" attribute, authors could conceivably design their
1168 own "document language" based on elements with almost no associated
1169 presentation (such as DIV and SPAN in HTML) and assigning style
1170 information through the "class" attribute. Authors should avoid this
1171 practice since the structural elements of a document language often
1172 have recognized and accepted meanings and author-defined classes may
1173 not.</p>
1174
1175 <p class="note"><strong>Note:</strong> If an element has multiple
1176 class attributes, their values must be concatenated with spaces
1177 between the values before searching for the class. As of this time the
1178 working group is not aware of any manner in which this situation can
1179 be reached, however, so this behavior is explicitly non-normative in
1180 this specification.</p>
1181
1182 <h3><a name=id-selectors>6.5. ID selectors</a></h3>
1183
1184 <p>Document languages may contain attributes that are declared to be
1185 of type ID. What makes attributes of type ID special is that no two
1186 such attributes can have the same value in a document, regardless of
1187 the type of the elements that carry them; whatever the document
1188 language, an ID typed attribute can be used to uniquely identify its
1189 element. In HTML all ID attributes are named "id"; XML applications
1190 may name ID attributes differently, but the same restriction
1191 applies.</p>
1192
1193 <p>An ID-typed attribute of a document language allows authors to
1194 assign an identifier to one element instance in the document tree. W3C
1195 ID selectors represent an element instance based on its identifier. An
1196 ID selector contains a &quot;number sign&quot; (U+0023,
1197 <code>#</code>) immediately followed by the ID value, which must be an
1198 identifier.</p>
1199
1200 <p>Selectors does not specify how a UA knows the ID-typed attribute of
1201 an element. The UA may, e.g., read a document's DTD, have the
1202 information hard-coded or ask the user.
1203
1204 <div class="example">
1205 <p>Examples:</p>
1206 <p>The following ID selector represents an <code>h1</code> element
1207 whose ID-typed attribute has the value "chapter1":</p>
1208 <pre>h1#chapter1</pre>
1209 <p>The following ID selector represents any element whose ID-typed
1210 attribute has the value "chapter1":</p>
1211 <pre>#chapter1</pre>
1212 <p>The following selector represents any element whose ID-typed
1213 attribute has the value "z98y".</p>
1214 <pre>*#z98y</pre>
1215 </div>
1216
1217 <p class="note"><strong>Note.</strong> In XML 1.0 <a
1218 href="#refsXML10">[XML10]</a>, the information about which attribute
1219 contains an element's IDs is contained in a DTD or a schema. When
1220 parsing XML, UAs do not always read the DTD, and thus may not know
1221 what the ID of an element is (though a UA may have namespace-specific
1222 knowledge that allows it to determine which attribute is the ID
1223 attribute for that namespace). If a style sheet designer knows or
1224 suspects that a UA may not know what the ID of an element is, he
1225 should use normal attribute selectors instead:
1226 <code>[name=p371]</code> instead of <code>#p371</code>. Elements in
1227 XML 1.0 documents without a DTD do not have IDs at all.</p>
1228
1229 <p>If an element has multiple ID attributes, all of them must be
1230 treated as IDs for that element for the purposes of the ID
1231 selector. Such a situation could be reached using mixtures of xml:id,
1232 DOM3 Core, XML DTDs, and namespace-specific knowledge.</p>
1233
1234 <h3><a name=pseudo-classes>6.6. Pseudo-classes</a></h3>
1235
1236 <p>The pseudo-class concept is introduced to permit selection based on
1237 information that lies outside of the document tree or that cannot be
1238 expressed using the other simple selectors.</p>
1239
1240 <p>A pseudo-class always consists of a &quot;colon&quot;
1241 (<code>:</code>) followed by the name of the pseudo-class and
1242 optionally by a value between parentheses.</p>
1243
1244 <p>Pseudo-classes are allowed in all sequences of simple selectors
1245 contained in a selector. Pseudo-classes are allowed anywhere in
1246 sequences of simple selectors, after the leading type selector or
1247 universal selector (possibly omitted). Pseudo-class names are
1248 case-insensitive. Some pseudo-classes are mutually exclusive, while
1249 others can be applied simultaneously to the same
1250 element. Pseudo-classes may be dynamic, in the sense that an element
1251 may acquire or lose a pseudo-class while a user interacts with the
1252 document.</p>
1253
1254
1255 <h4><a name=dynamic-pseudos>6.6.1. Dynamic pseudo-classes</a></h4>
1256
1257 <p>Dynamic pseudo-classes classify elements on characteristics other
1258 than their name, attributes, or content, in principle characteristics
1259 that cannot be deduced from the document tree.</p>
1260
1261 <p>Dynamic pseudo-classes do not appear in the document source or
1262 document tree.</p>
1263
1264
1265 <h5>The <a name=link>link pseudo-classes: :link and :visited</a></h5>
1266
1267 <p>User agents commonly display unvisited links differently from
1268 previously visited ones. Selectors
1269 provides the pseudo-classes <code>:link</code> and
1270 <code>:visited</code> to distinguish them:</p>
1271
1272 <ul>
1273 <li>The <code>:link</code> pseudo-class applies to links that have
1274 not yet been visited.</li>
1275 <li>The <code>:visited</code> pseudo-class applies once the link has
1276 been visited by the user. </li>
1277 </ul>
1278
1279 <p>After some amount of time, user agents may choose to return a
1280 visited link to the (unvisited) ':link' state.</p>
1281
1282 <p>The two states are mutually exclusive.</p>
1283
1284 <div class="example">
1285
1286 <p>Example:</p>
1287
1288 <p>The following selector represents links carrying class
1289 <code>external</code> and already visited:</p>
1290
1291 <pre>a.external:visited</pre>
1292
1293 </div>
1294
1295 <p class="note"><strong>Note:</strong> It is possible for style sheet
1296 authors to abuse the :link and :visited pseudo-classes to determine
1297 which sites a user has visited without the user's consent.
1298
1299 <p>UAs may therefore treat all links as unvisited links, or implement
1300 other measures to preserve the user's privacy while rendering visited
1301 and unvisited links differently.</p>
1302
1303 <h5>The <a name=useraction-pseudos>user action pseudo-classes
1304 :hover, :active, and :focus</a></h5>
1305
1306 <p>Interactive user agents sometimes change the rendering in response
1307 to user actions. Selectors provides
1308 three pseudo-classes for the selection of an element the user is
1309 acting on.</p>
1310
1311 <ul>
1312
1313 <li>The <code>:hover</code> pseudo-class applies while the user
1314 designates an element with a pointing device, but does not activate
1315 it. For example, a visual user agent could apply this pseudo-class
1316 when the cursor (mouse pointer) hovers over a box generated by the
1317 element. User agents not that do not support <a
1318 href="http://www.w3.org/TR/REC-CSS2/media.html#interactive-media-group">intera ctive
1319 media</a> do not have to support this pseudo-class. Some conforming
1320 user agents that support <a
1321 href="http://www.w3.org/TR/REC-CSS2/media.html#interactive-media-group">intera ctive
1322 media</a> may not be able to support this pseudo-class (e.g., a pen
1323 device that does not detect hovering).</li>
1324
1325 <li>The <code>:active</code> pseudo-class applies while an element
1326 is being activated by the user. For example, between the times the
1327 user presses the mouse button and releases it.</li>
1328
1329 <li>The <code>:focus</code> pseudo-class applies while an element
1330 has the focus (accepts keyboard or mouse events, or other forms of
1331 input). </li>
1332
1333 </ul>
1334
1335 <p>There may be document language or implementation specific limits on
1336 which elements can become <code>:active</code> or acquire
1337 <code>:focus</code>.</p>
1338
1339 <p>These pseudo-classes are not mutually exclusive. An element may
1340 match several pseudo-classes at the same time.</p>
1341
1342 <p>Selectors doesn't define if the parent of an element that is
1343 ':active' or ':hover' is also in that state.</p>
1344
1345 <div class="example">
1346 <p>Examples:</p>
1347 <pre>a:link /* unvisited links */
1348 a:visited /* visited links */
1349 a:hover /* user hovers */
1350 a:active /* active links */</pre>
1351 <p>An example of combining dynamic pseudo-classes:</p>
1352 <pre>a:focus
1353 a:focus:hover</pre>
1354 <p>The last selector matches <code>a</code> elements that are in
1355 the pseudo-class :focus and in the pseudo-class :hover.</p>
1356 </div>
1357
1358 <p class="note"><strong>Note:</strong> An element can be both ':visited'
1359 and ':active' (or ':link' and ':active').</p>
1360
1361 <h4><a name=target-pseudo>6.6.2. The target pseudo-class :target</a></h4>
1362
1363 <p>Some URIs refer to a location within a resource. This kind of URI
1364 ends with a &quot;number sign&quot; (#) followed by an anchor
1365 identifier (called the fragment identifier).</p>
1366
1367 <p>URIs with fragment identifiers link to a certain element within the
1368 document, known as the target element. For instance, here is a URI
1369 pointing to an anchor named <code>section_2</code> in an HTML
1370 document:</p>
1371
1372 <pre>http://example.com/html/top.html#section_2</pre>
1373
1374 <p>A target element can be represented by the <code>:target</code>
1375 pseudo-class. If the document's URI has no fragment identifier, then
1376 the document has no target element.</p>
1377
1378 <div class="example">
1379 <p>Example:</p>
1380 <pre>p.note:target</pre>
1381 <p>This selector represents a <code>p</code> element of class
1382 <code>note</code> that is the target element of the referring
1383 URI.</p>
1384 </div>
1385
1386 <div class="example">
1387 <p>CSS example:</p>
1388 <p>Here, the <code>:target</code> pseudo-class is used to make the
1389 target element red and place an image before it, if there is one:</p>
1390 <pre>*:target { color : red }
1391 *:target::before { content : url(target.png) }</pre>
1392 </div>
1393
1394 <h4><a name=lang-pseudo>6.6.3. The language pseudo-class :lang</a></h4>
1395
1396 <p>If the document language specifies how the human language of an
1397 element is determined, it is possible to write selectors that
1398 represent an element based on its language. For example, in HTML <a
1399 href="#refsHTML4">[HTML4]</a>, the language is determined by a
1400 combination of the <code>lang</code> attribute, the <code>meta</code>
1401 element, and possibly by information from the protocol (such as HTTP
1402 headers). XML uses an attribute called <code>xml:lang</code>, and
1403 there may be other document language-specific methods for determining
1404 the language.</p>
1405
1406 <p>The pseudo-class <code>:lang(C)</code> represents an element that
1407 is in language C. Whether an element is represented by a
1408 <code>:lang()</code> selector is based solely on the identifier C
1409 being either equal to, or a hyphen-separated substring of, the
1410 element's language value, in the same way as if performed by the <a
1411 href="#attribute-representation">'|='</a> operator in attribute
1412 selectors. The identifier C does not have to be a valid language
1413 name.</p>
1414
1415 <p>C must not be empty. (If it is, the selector is invalid.)</p>
1416
1417 <p class="note"><strong>Note:</strong> It is recommended that
1418 documents and protocols indicate language using codes from RFC 3066 <a
1419 href="#refsRFC3066">[RFC3066]</a> or its successor, and by means of
1420 "xml:lang" attributes in the case of XML-based documents <a
1421 href="#refsXML10">[XML10]</a>. See <a
1422 href="http://www.w3.org/International/questions/qa-lang-2or3.html">
1423 "FAQ: Two-letter or three-letter language codes."</a></p>
1424
1425 <div class="example">
1426 <p>Examples:</p>
1427 <p>The two following selectors represent an HTML document that is in
1428 Belgian, French, or German. The two next selectors represent
1429 <code>q</code> quotations in an arbitrary element in Belgian, French,
1430 or German.</p>
1431 <pre>html:lang(fr-be)
1432 html:lang(de)
1433 :lang(fr-be) &gt; q
1434 :lang(de) &gt; q</pre>
1435 </div>
1436
1437 <h4><a name=UIstates>6.6.4. The UI element states pseudo-classes</a></h4>
1438
1439 <h5><a name=enableddisabled>The :enabled and :disabled pseudo-classes</a></h5>
1440
1441 <p>The <code>:enabled</code> pseudo-class allows authors to customize
1442 the look of user interface elements that are enabled &mdash; which the
1443 user can select or activate in some fashion (e.g. clicking on a button
1444 with a mouse). There is a need for such a pseudo-class because there
1445 is no way to programmatically specify the default appearance of say,
1446 an enabled <code>input</code> element without also specifying what it
1447 would look like when it was disabled.</p>
1448
1449 <p>Similar to <code>:enabled</code>, <code>:disabled</code> allows the
1450 author to specify precisely how a disabled or inactive user interface
1451 element should look.</p>
1452
1453 <p>Most elements will be neither enabled nor disabled. An element is
1454 enabled if the user can either activate it or transfer the focus to
1455 it. An element is disabled if it could be enabled, but the user cannot
1456 presently activate it or transfer focus to it.</p>
1457
1458
1459 <h5><a name=checked>The :checked pseudo-class</a></h5>
1460
1461 <p>Radio and checkbox elements can be toggled by the user. Some menu
1462 items are "checked" when the user selects them. When such elements are
1463 toggled "on" the <code>:checked</code> pseudo-class applies. The
1464 <code>:checked</code> pseudo-class initially applies to such elements
1465 that have the HTML4 <code>selected</code> and <code>checked</code>
1466 attributes as described in <a
1467 href="http://www.w3.org/TR/REC-html40/interact/forms.html#h-17.2.1">Section
1468 17.2.1 of HTML4</a>, but of course the user can toggle "off" such
1469 elements in which case the <code>:checked</code> pseudo-class would no
1470 longer apply. While the <code>:checked</code> pseudo-class is dynamic
1471 in nature, and is altered by user action, since it can also be based
1472 on the presence of the semantic HTML4 <code>selected</code> and
1473 <code>checked</code> attributes, it applies to all media.
1474
1475
1476 <h5><a name=indeterminate>The :indeterminate pseudo-class</a></h5>
1477
1478 <div class="note">
1479
1480 <p>Radio and checkbox elements can be toggled by the user, but are
1481 sometimes in an indeterminate state, neither checked nor unchecked.
1482 This can be due to an element attribute, or DOM manipulation.</p>
1483
1484 <p>A future version of this specification may introduce an
1485 <code>:indeterminate</code> pseudo-class that applies to such elements.
1486 <!--While the <code>:indeterminate</code> pseudo-class is dynamic in
1487 nature, and is altered by user action, since it can also be based on
1488 the presence of an element attribute, it applies to all media.</p>
1489
1490 <p>Components of a radio-group initialized with no pre-selected choice
1491 are an example of :indeterminate state.--></p>
1492
1493 </div>
1494
1495
1496 <h4><a name=structural-pseudos>6.6.5. Structural pseudo-classes</a></h4>
1497
1498 <p>Selectors introduces the concept of <dfn>structural
1499 pseudo-classes</dfn> to permit selection based on extra information that lies in
1500 the document tree but cannot be represented by other simple selectors or
1501 combinators.
1502
1503 <p>Note that standalone pieces of PCDATA (text nodes in the DOM) are
1504 not counted when calculating the position of an element in the list of
1505 children of its parent. When calculating the position of an element in
1506 the list of children of its parent, the index numbering starts at 1.
1507
1508
1509 <h5><a name=root-pseudo>:root pseudo-class</a></h5>
1510
1511 <p>The <code>:root</code> pseudo-class represents an element that is
1512 the root of the document. In HTML 4, this is always the
1513 <code>HTML</code> element.
1514
1515
1516 <h5><a name=nth-child-pseudo>:nth-child() pseudo-class</a></h5>
1517
1518 <p>The
1519 <code>:nth-child(<var>a</var><code>n</code>+<var>b</var>)</code>
1520 pseudo-class notation represents an element that has
1521 <var>a</var><code>n</code>+<var>b</var>-1 siblings
1522 <strong>before</strong> it in the document tree, for a given positive
1523 integer or zero value of <code>n</code>, and has a parent element. In
1524 other words, this matches the <var>b</var>th child of an element after
1525 all the children have been split into groups of <var>a</var> elements
1526 each. For example, this allows the selectors to address every other
1527 row in a table, and could be used to alternate the color
1528 of paragraph text in a cycle of four. The <var>a</var> and
1529 <var>b</var> values must be zero, negative integers or positive
1530 integers. The index of the first child of an element is 1.
1531
1532 <p>In addition to this, <code>:nth-child()</code> can take
1533 '<code>odd</code>' and '<code>even</code>' as arguments instead.
1534 '<code>odd</code>' has the same signification as <code>2n+1</code>,
1535 and '<code>even</code>' has the same signification as <code>2n</code>.
1536
1537
1538 <div class="example">
1539 <p>Examples:</p>
1540 <pre>tr:nth-child(2n+1) /* represents every odd row of an HTML table */
1541 tr:nth-child(odd) /* same */
1542 tr:nth-child(2n) /* represents every even row of an HTML table */
1543 tr:nth-child(even) /* same */
1544
1545 /* Alternate paragraph colours in CSS */
1546 p:nth-child(4n+1) { color: navy; }
1547 p:nth-child(4n+2) { color: green; }
1548 p:nth-child(4n+3) { color: maroon; }
1549 p:nth-child(4n+4) { color: purple; }</pre>
1550 </div>
1551
1552 <p>When <var>a</var>=0, no repeating is used, so for example
1553 <code>:nth-child(0n+5)</code> matches only the fifth child. When
1554 <var>a</var>=0, the <var>a</var><code>n</code> part need not be
1555 included, so the syntax simplifies to
1556 <code>:nth-child(<var>b</var>)</code> and the last example simplifies
1557 to <code>:nth-child(5)</code>.
1558
1559 <div class="example">
1560 <p>Examples:</p>
1561 <pre>foo:nth-child(0n+1) /* represents an element foo, first child of its pare nt element */
1562 foo:nth-child(1) /* same */</pre>
1563 </div>
1564
1565 <p>When <var>a</var>=1, the number may be omitted from the rule.
1566
1567 <div class="example">
1568 <p>Examples:</p>
1569 <p>The following selectors are therefore equivalent:</p>
1570 <pre>bar:nth-child(1n+0) /* represents all bar elements, specificity (0,1,1) * /
1571 bar:nth-child(n+0) /* same */
1572 bar:nth-child(n) /* same */
1573 bar /* same but lower specificity (0,0,1) */</pre>
1574 </div>
1575
1576 <p>If <var>b</var>=0, then every <var>a</var>th element is picked. In
1577 such a case, the <var>b</var> part may be omitted.
1578
1579 <div class="example">
1580 <p>Examples:</p>
1581 <pre>tr:nth-child(2n+0) /* represents every even row of an HTML table */
1582 tr:nth-child(2n) /* same */</pre>
1583 </div>
1584
1585 <p>If both <var>a</var> and <var>b</var> are equal to zero, the
1586 pseudo-class represents no element in the document tree.</p>
1587
1588 <p>The value <var>a</var> can be negative, but only the positive
1589 values of <var>a</var><code>n</code>+<var>b</var>, for
1590 <code>n</code>&ge;0, may represent an element in the document
1591 tree.</p>
1592
1593 <div class="example">
1594 <p>Example:</p>
1595 <pre>html|tr:nth-child(-n+6) /* represents the 6 first rows of XHTML tables */< /pre>
1596 </div>
1597
1598 <p>When the value <var>b</var> is negative, the "+" character in the
1599 expression must be removed (it is effectively replaced by the "-"
1600 character indicating the negative value of <var>b</var>).</p>
1601
1602 <div class="example">
1603 <p>Examples:</p>
1604 <pre>:nth-child(10n-1) /* represents the 9th, 19th, 29th, etc, element */
1605 :nth-child(10n+9) /* Same */
1606 :nth-child(10n+-1) /* Syntactically invalid, and would be ignored */</pre>
1607 </div>
1608
1609
1610 <h5><a name=nth-last-child-pseudo>:nth-last-child() pseudo-class</a></h5>
1611
1612 <p>The <code>:nth-last-child(<var>a</var>n+<var>b</var>)</code>
1613 pseudo-class notation represents an element that has
1614 <var>a</var><code>n</code>+<var>b</var>-1 siblings
1615 <strong>after</strong> it in the document tree, for a given positive
1616 integer or zero value of <code>n</code>, and has a parent element. See
1617 <code>:nth-child()</code> pseudo-class for the syntax of its argument.
1618 It also accepts the '<code>even</code>' and '<code>odd</code>' values
1619 as arguments.
1620
1621
1622 <div class="example">
1623 <p>Examples:</p>
1624 <pre>tr:nth-last-child(-n+2) /* represents the two last rows of an HTML table */
1625
1626 foo:nth-last-child(odd) /* represents all odd foo elements in their parent el ement,
1627 counting from the last one */</pre>
1628 </div>
1629
1630
1631 <h5><a name=nth-of-type-pseudo>:nth-of-type() pseudo-class</a></h5>
1632
1633 <p>The <code>:nth-of-type(<var>a</var>n+<var>b</var>)</code>
1634 pseudo-class notation represents an element that has
1635 <var>a</var><code>n</code>+<var>b</var>-1 siblings with the same
1636 element name <strong>before</strong> it in the document tree, for a
1637 given zero or positive integer value of <code>n</code>, and has a
1638 parent element. In other words, this matches the <var>b</var>th child
1639 of that type after all the children of that type have been split into
1640 groups of a elements each. See <code>:nth-child()</code> pseudo-class
1641 for the syntax of its argument. It also accepts the
1642 '<code>even</code>' and '<code>odd</code>' values.
1643
1644
1645 <div class="example">
1646 <p>CSS example:</p>
1647 <p>This allows an author to alternate the position of floated images:</p>
1648 <pre>img:nth-of-type(2n+1) { float: right; }
1649 img:nth-of-type(2n) { float: left; }</pre>
1650 </div>
1651
1652
1653 <h5><a name=nth-last-of-type-pseudo>:nth-last-of-type() pseudo-class</a></h5>
1654
1655 <p>The <code>:nth-last-of-type(<var>a</var>n+<var>b</var>)</code>
1656 pseudo-class notation represents an element that has
1657 <var>a</var><code>n</code>+<var>b</var>-1 siblings with the same
1658 element name <strong>after</strong> it in the document tree, for a
1659 given zero or positive integer value of <code>n</code>, and has a
1660 parent element. See <code>:nth-child()</code> pseudo-class for the
1661 syntax of its argument. It also accepts the '<code>even</code>' and '<code>odd</ code>' values.
1662
1663
1664 <div class="example">
1665 <p>Example:</p>
1666 <p>To represent all <code>h2</code> children of an XHTML
1667 <code>body</code> except the first and last, one could use the
1668 following selector:</p>
1669 <pre>body &gt; h2:nth-of-type(n+2):nth-last-of-type(n+2)</pre>
1670 <p>In this case, one could also use <code>:not()</code>, although the
1671 selector ends up being just as long:</p>
1672 <pre>body &gt; h2:not(:first-of-type):not(:last-of-type)</pre>
1673 </div>
1674
1675
1676 <h5><a name=first-child-pseudo>:first-child pseudo-class</a></h5>
1677
1678 <p>Same as <code>:nth-child(1)</code>. The <code>:first-child</code> pseudo-clas s
1679 represents an element that is the first child of some other element.
1680
1681
1682 <div class="example">
1683 <p>Examples:</p>
1684 <p>The following selector represents a <code>p</code> element that is
1685 the first child of a <code>div</code> element:</p>
1686 <pre>div &gt; p:first-child</pre>
1687 <p>This selector can represent the <code>p</code> inside the
1688 <code>div</code> of the following fragment:</p>
1689 <pre>&lt;p&gt; The last P before the note.&lt;/p&gt;
1690 &lt;div class="note"&gt;
1691 &lt;p&gt; The first P inside the note.&lt;/p&gt;
1692 &lt;/div&gt;</pre>but cannot represent the second <code>p</code> in the followin g
1693 fragment:
1694 <pre>&lt;p&gt; The last P before the note.&lt;/p&gt;
1695 &lt;div class="note"&gt;
1696 &lt;h2&gt; Note &lt;/h2&gt;
1697 &lt;p&gt; The first P inside the note.&lt;/p&gt;
1698 &lt;/div&gt;</pre>
1699 <p>The following two selectors are usually equivalent:</p>
1700 <pre>* &gt; a:first-child /* a is first child of any element */
1701 a:first-child /* Same (assuming a is not the root element) */</pre>
1702 </div>
1703
1704 <h5><a name=last-child-pseudo>:last-child pseudo-class</a></h5>
1705
1706 <p>Same as <code>:nth-last-child(1)</code>. The <code>:last-child</code> pseudo- class
1707 represents an element that is the last child of some other element.
1708
1709 <div class="example">
1710 <p>Example:</p>
1711 <p>The following selector represents a list item <code>li</code> that
1712 is the last child of an ordered list <code>ol</code>.
1713 <pre>ol &gt; li:last-child</pre>
1714 </div>
1715
1716 <h5><a name=first-of-type-pseudo>:first-of-type pseudo-class</a></h5>
1717
1718 <p>Same as <code>:nth-of-type(1)</code>. The <code>:first-of-type</code> pseudo- class
1719 represents an element that is the first sibling of its type in the list of
1720 children of its parent element.
1721
1722 <div class="example">
1723 <p>Example:</p>
1724 <p>The following selector represents a definition title
1725 <code>dt</code> inside a definition list <code>dl</code>, this
1726 <code>dt</code> being the first of its type in the list of children of
1727 its parent element.</p>
1728 <pre>dl dt:first-of-type</pre>
1729 <p>It is a valid description for the first two <code>dt</code>
1730 elements in the following example but not for the third one:</p>
1731 <pre>&lt;dl&gt;
1732 &lt;dt&gt;gigogne&lt;/dt&gt;
1733 &lt;dd&gt;
1734 &lt;dl&gt;
1735 &lt;dt&gt;fus&eacute;e&lt;/dt&gt;
1736 &lt;dd&gt;multistage rocket&lt;/dd&gt;
1737 &lt;dt&gt;table&lt;/dt&gt;
1738 &lt;dd&gt;nest of tables&lt;/dd&gt;
1739 &lt;/dl&gt;
1740 &lt;/dd&gt;
1741 &lt;/dl&gt;</pre>
1742 </div>
1743
1744 <h5><a name=last-of-type-pseudo>:last-of-type pseudo-class</a></h5>
1745
1746 <p>Same as <code>:nth-last-of-type(1)</code>. The
1747 <code>:last-of-type</code> pseudo-class represents an element that is
1748 the last sibling of its type in the list of children of its parent
1749 element.</p>
1750
1751 <div class="example">
1752 <p>Example:</p>
1753 <p>The following selector represents the last data cell
1754 <code>td</code> of a table row.</p>
1755 <pre>tr &gt; td:last-of-type</pre>
1756 </div>
1757
1758 <h5><a name=only-child-pseudo>:only-child pseudo-class</a></h5>
1759
1760 <p>Represents an element that has a parent element and whose parent
1761 element has no other element children. Same as
1762 <code>:first-child:last-child</code> or
1763 <code>:nth-child(1):nth-last-child(1)</code>, but with a lower
1764 specificity.</p>
1765
1766 <h5><a name=only-of-type-pseudo>:only-of-type pseudo-class</a></h5>
1767
1768 <p>Represents an element that has a parent element and whose parent
1769 element has no other element children with the same element name. Same
1770 as <code>:first-of-type:last-of-type</code> or
1771 <code>:nth-of-type(1):nth-last-of-type(1)</code>, but with a lower
1772 specificity.</p>
1773
1774
1775 <h5><a name=empty-pseudo></a>:empty pseudo-class</h5>
1776
1777 <p>The <code>:empty</code> pseudo-class represents an element that has
1778 no children at all. In terms of the DOM, only element nodes and text
1779 nodes (including CDATA nodes and entity references) whose data has a
1780 non-zero length must be considered as affecting emptiness; comments,
1781 PIs, and other nodes must not affect whether an element is considered
1782 empty or not.</p>
1783
1784 <div class="example">
1785 <p>Examples:</p>
1786 <p><code>p:empty</code> is a valid representation of the following fragment:</p >
1787 <pre>&lt;p&gt;&lt;/p&gt;</pre>
1788 <p><code>foo:empty</code> is not a valid representation for the
1789 following fragments:</p>
1790 <pre>&lt;foo&gt;bar&lt;/foo&gt;</pre>
1791 <pre>&lt;foo&gt;&lt;bar&gt;bla&lt;/bar&gt;&lt;/foo&gt;</pre>
1792 <pre>&lt;foo&gt;this is not &lt;bar&gt;:empty&lt;/bar&gt;&lt;/foo&gt;</pre>
1793 </div>
1794
1795 <h4><a name=content-selectors>6.6.6. Blank</a></h4> <!-- It's the Return of Appe ndix H!!! Run away! -->
1796
1797 <p>This section intentionally left blank.</p>
1798 <!-- (used to be :contains()) -->
1799
1800 <h4><a name=negation></a>6.6.7. The negation pseudo-class</h4>
1801
1802 <p>The negation pseudo-class, <code>:not(<var>X</var>)</code>, is a
1803 functional notation taking a <a href="#simple-selectors-dfn">simple
1804 selector</a> (excluding the negation pseudo-class itself and
1805 pseudo-elements) as an argument. It represents an element that is not
1806 represented by the argument.
1807
1808 <!-- pseudo-elements are not simple selectors, so the above paragraph
1809 may be a bit confusing -->
1810
1811 <div class="example">
1812 <p>Examples:</p>
1813 <p>The following CSS selector matches all <code>button</code>
1814 elements in an HTML document that are not disabled.</p>
1815 <pre>button:not([DISABLED])</pre>
1816 <p>The following selector represents all but <code>FOO</code>
1817 elements.</p>
1818 <pre>*:not(FOO)</pre>
1819 <p>The following group of selectors represents all HTML elements
1820 except links.</p>
1821 <pre>html|*:not(:link):not(:visited)</pre>
1822 </div>
1823
1824 <p>Default namespace declarations do not affect the argument of the
1825 negation pseudo-class unless the argument is a universal selector or a
1826 type selector.</p>
1827
1828 <div class="example">
1829 <p>Examples:</p>
1830 <p>Assuming that the default namespace is bound to
1831 "http://example.com/", the following selector represents all
1832 elements that are not in that namespace:</p>
1833 <pre>*|*:not(*)</pre>
1834 <p>The following CSS selector matches any element being hovered,
1835 regardless of its namespace. In particular, it is not limited to
1836 only matching elements in the default namespace that are not being
1837 hovered, and elements not in the default namespace don't match the
1838 rule when they <em>are</em> being hovered.</p>
1839 <pre>*|*:not(:hover)</pre>
1840 </div>
1841
1842 <p class="note"><strong>Note</strong>: the :not() pseudo allows
1843 useless selectors to be written. For instance <code>:not(*|*)</code>,
1844 which represents no element at all, or <code>foo:not(bar)</code>,
1845 which is equivalent to <code>foo</code> but with a higher
1846 specificity.</p>
1847
1848 <h3><a name=pseudo-elements>7. Pseudo-elements</a></h3>
1849
1850 <p>Pseudo-elements create abstractions about the document tree beyond
1851 those specified by the document language. For instance, document
1852 languages do not offer mechanisms to access the first letter or first
1853 line of an element's content. Pseudo-elements allow designers to refer
1854 to this otherwise inaccessible information. Pseudo-elements may also
1855 provide designers a way to refer to content that does not exist in the
1856 source document (e.g., the <code>::before</code> and
1857 <code>::after</code> pseudo-elements give access to generated
1858 content).</p>
1859
1860 <p>A pseudo-element is made of two colons (<code>::</code>) followed
1861 by the name of the pseudo-element.</p>
1862
1863 <p>This <code>::</code> notation is introduced by the current document
1864 in order to establish a discrimination between pseudo-classes and
1865 pseudo-elements. For compatibility with existing style sheets, user
1866 agents must also accept the previous one-colon notation for
1867 pseudo-elements introduced in CSS levels 1 and 2 (namely,
1868 <code>:first-line</code>, <code>:first-letter</code>,
1869 <code>:before</code> and <code>:after</code>). This compatibility is
1870 not allowed for the new pseudo-elements introduced in CSS level 3.</p>
1871
1872 <p>Only one pseudo-element may appear per selector, and if present it
1873 must appear after the sequence of simple selectors that represents the
1874 <a href="#subject">subjects</a> of the selector. <span class="note">A
1875 future version of this specification may allow multiple
1876 pesudo-elements per selector.</span></p>
1877
1878 <h4><a name=first-line>7.1. The ::first-line pseudo-element</a></h4>
1879
1880 <p>The <code>::first-line</code> pseudo-element describes the contents
1881 of the first formatted line of an element.
1882
1883 <div class="example">
1884 <p>CSS example:</p>
1885 <pre>p::first-line { text-transform: uppercase }</pre>
1886 <p>The above rule means "change the letters of the first line of every
1887 paragraph to uppercase".</p>
1888 </div>
1889
1890 <p>The selector <code>p::first-line</code> does not match any real
1891 HTML element. It does match a pseudo-element that conforming user
1892 agents will insert at the beginning of every paragraph.</p>
1893
1894 <p>Note that the length of the first line depends on a number of
1895 factors, including the width of the page, the font size, etc. Thus,
1896 an ordinary HTML paragraph such as:</p>
1897
1898 <pre>
1899 &lt;P&gt;This is a somewhat long HTML
1900 paragraph that will be broken into several
1901 lines. The first line will be identified
1902 by a fictional tag sequence. The other lines
1903 will be treated as ordinary lines in the
1904 paragraph.&lt;/P&gt;
1905 </pre>
1906
1907 <p>the lines of which happen to be broken as follows:
1908
1909 <pre>
1910 THIS IS A SOMEWHAT LONG HTML PARAGRAPH THAT
1911 will be broken into several lines. The first
1912 line will be identified by a fictional tag
1913 sequence. The other lines will be treated as
1914 ordinary lines in the paragraph.
1915 </pre>
1916
1917 <p>This paragraph might be "rewritten" by user agents to include the
1918 <em>fictional tag sequence</em> for <code>::first-line</code>. This
1919 fictional tag sequence helps to show how properties are inherited.</p>
1920
1921 <pre>
1922 &lt;P&gt;<b>&lt;P::first-line&gt;</b> This is a somewhat long HTML
1923 paragraph that <b>&lt;/P::first-line&gt;</b> will be broken into several
1924 lines. The first line will be identified
1925 by a fictional tag sequence. The other lines
1926 will be treated as ordinary lines in the
1927 paragraph.&lt;/P&gt;
1928 </pre>
1929
1930 <p>If a pseudo-element breaks up a real element, the desired effect
1931 can often be described by a fictional tag sequence that closes and
1932 then re-opens the element. Thus, if we mark up the previous paragraph
1933 with a <code>span</code> element:</p>
1934
1935 <pre>
1936 &lt;P&gt;<b>&lt;SPAN class="test"&gt;</b> This is a somewhat long HTML
1937 paragraph that will be broken into several
1938 lines.<b>&lt;/SPAN&gt;</b> The first line will be identified
1939 by a fictional tag sequence. The other lines
1940 will be treated as ordinary lines in the
1941 paragraph.&lt;/P&gt;
1942 </pre>
1943
1944 <p>the user agent could simulate start and end tags for
1945 <code>span</code> when inserting the fictional tag sequence for
1946 <code>::first-line</code>.
1947
1948 <pre>
1949 &lt;P&gt;&lt;P::first-line&gt;<b>&lt;SPAN class="test"&gt;</b> This is a
1950 somewhat long HTML
1951 paragraph that will <b>&lt;/SPAN&gt;</b>&lt;/P::first-line&gt;<b>&lt;SPAN class= "test"&gt;</b> be
1952 broken into several
1953 lines.<b>&lt;/SPAN&gt;</b> The first line will be identified
1954 by a fictional tag sequence. The other lines
1955 will be treated as ordinary lines in the
1956 paragraph.&lt;/P&gt;
1957 </pre>
1958
1959 <p>In CSS, the <code>::first-line</code> pseudo-element can only be
1960 attached to a block-level element, an inline-block, a table-caption,
1961 or a table-cell.</p>
1962
1963 <p><a name="first-formatted-line"></a>The "first formatted line" of an
1964 element may occur inside a
1965 block-level descendant in the same flow (i.e., a block-level
1966 descendant that is not positioned and not a float). E.g., the first
1967 line of the <code>div</code> in <code>&lt;DIV>&lt;P>This
1968 line...&lt;/P>&lt/DIV></code> is the first line of the <code>p</code> (assuming
1969 that both <code>p</code> and <code>div</code> are block-level).
1970
1971 <p>The first line of a table-cell or inline-block cannot be the first
1972 formatted line of an ancestor element. Thus, in <code>&lt;DIV&gt;&lt;P
1973 STYLE="display: inline-block">Hello&lt;BR&gt;Goodbye&lt;/P&gt;
1974 etcetera&lt;/DIV&gt;</code> the first formatted line of the
1975 <code>div</code> is not the line "Hello".
1976
1977 <p class="note">Note that the first line of the <code>p</code> in this
1978 fragment: <code>&lt;p&gt&lt;br&gt;First...</code> doesn't contain any
1979 letters (assuming the default style for <code>br</code> in HTML
1980 4). The word "First" is not on the first formatted line.
1981
1982 <p>A UA should act as if the fictional start tags of the
1983 <code>::first-line</code> pseudo-elements were nested just inside the
1984 innermost enclosing block-level element. (Since CSS1 and CSS2 were
1985 silent on this case, authors should not rely on this behavior.) Here
1986 is an example. The fictional tag sequence for</p>
1987
1988 <pre>
1989 &lt;DIV>
1990 &lt;P>First paragraph&lt;/P>
1991 &lt;P>Second paragraph&lt;/P>
1992 &lt;/DIV>
1993 </pre>
1994
1995 <p>is</p>
1996
1997 <pre>
1998 &lt;DIV>
1999 &lt;P>&lt;DIV::first-line>&lt;P::first-line>First paragraph&lt;/P::first-line> &lt;/DIV::first-line>&lt;/P>
2000 &lt;P>&lt;P::first-line>Second paragraph&lt;/P::first-line>&lt;/P>
2001 &lt;/DIV>
2002 </pre>
2003
2004 <p>The <code>::first-line</code> pseudo-element is similar to an
2005 inline-level element, but with certain restrictions. In CSS, the
2006 following properties apply to a <code>::first-line</code>
2007 pseudo-element: font properties, color property, background
2008 properties, 'word-spacing', 'letter-spacing', 'text-decoration',
2009 'vertical-align', 'text-transform', 'line-height'. UAs may apply other
2010 properties as well.</p>
2011
2012
2013 <h4><a name=first-letter>7.2. The ::first-letter pseudo-element</a></h4>
2014
2015 <p>The <code>::first-letter</code> pseudo-element represents the first
2016 letter of the first line of a block, if it is not preceded by any
2017 other content (such as images or inline tables) on its line. The
2018 ::first-letter pseudo-element may be used for "initial caps" and "drop
2019 caps", which are common typographical effects. This type of initial
2020 letter is similar to an inline-level element if its 'float' property
2021 is 'none'; otherwise, it is similar to a floated element.</p>
2022
2023 <p>In CSS, these are the properties that apply to <code>::first-letter</code>
2024 pseudo-elements: font properties, 'text-decoration', 'text-transform',
2025 'letter-spacing', 'word-spacing' (when appropriate), 'line-height',
2026 'float', 'vertical-align' (only if 'float' is 'none'), margin
2027 properties, padding properties, border properties, color property,
2028 background properties. UAs may apply other properties as well. To
2029 allow UAs to render a typographically correct drop cap or initial cap,
2030 the UA may choose a line-height, width and height based on the shape
2031 of the letter, unlike for normal elements.</p>
2032
2033 <div class="example">
2034 <p>Example:</p>
2035 <p>This example shows a possible rendering of an initial cap. Note
2036 that the 'line-height' that is inherited by the <code>::first-letter</code>
2037 pseudo-element is 1.1, but the UA in this example has computed the
2038 height of the first letter differently, so that it doesn't cause any
2039 unnecessary space between the first two lines. Also note that the
2040 fictional start tag of the first letter is inside the <span>span</span>, and thu s
2041 the font weight of the first letter is normal, not bold as the <span>span</span> :
2042 <pre>
2043 p { line-height: 1.1 }
2044 p::first-letter { font-size: 3em; font-weight: normal }
2045 span { font-weight: bold }
2046 ...
2047 &lt;p>&lt;span>Het hemelsche&lt;/span> gerecht heeft zich ten lange lesten&lt;br >
2048 Erbarremt over my en mijn benaeuwde vesten&lt;br>
2049 En arme burgery, en op mijn volcx gebed&lt;br>
2050 En dagelix geschrey de bange stad ontzet.
2051 </pre>
2052 <div class="figure">
2053 <p><img src="initial-cap.png" alt="Image illustrating the ::first-letter pseudo- element">
2054 </div>
2055 </div>
2056
2057 <div class="example">
2058 <p>The following CSS will make a drop cap initial letter span about two lines:</ p>
2059
2060 <pre>
2061 &lt;!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"&gt;
2062 &lt;HTML&gt;
2063 &lt;HEAD&gt;
2064 &lt;TITLE&gt;Drop cap initial letter&lt;/TITLE&gt;
2065 &lt;STYLE type="text/css"&gt;
2066 P { font-size: 12pt; line-height: 1.2 }
2067 P::first-letter { font-size: 200%; font-weight: bold; float: left }
2068 SPAN { text-transform: uppercase }
2069 &lt;/STYLE&gt;
2070 &lt;/HEAD&gt;
2071 &lt;BODY&gt;
2072 &lt;P&gt;&lt;SPAN&gt;The first&lt;/SPAN&gt; few words of an article
2073 in The Economist.&lt;/P&gt;
2074 &lt;/BODY&gt;
2075 &lt;/HTML&gt;
2076 </pre>
2077
2078 <p>This example might be formatted as follows:</p>
2079
2080 <div class="figure">
2081 <P><img src="first-letter.gif" alt="Image illustrating the combined effect of th e ::first-letter and ::first-line pseudo-elements"></p>
2082 </div>
2083
2084 <p>The <span class="index-inst" title="fictional tag
2085 sequence">fictional tag sequence</span> is:</p>
2086
2087 <pre>
2088 &lt;P&gt;
2089 &lt;SPAN&gt;
2090 &lt;P::first-letter&gt;
2091 T
2092 &lt;/P::first-letter&gt;he first
2093 &lt;/SPAN&gt;
2094 few words of an article in the Economist.
2095 &lt;/P&gt;
2096 </pre>
2097
2098 <p>Note that the <code>::first-letter</code> pseudo-element tags abut
2099 the content (i.e., the initial character), while the ::first-line
2100 pseudo-element start tag is inserted right after the start tag of the
2101 block element.</p> </div>
2102
2103 <p>In order to achieve traditional drop caps formatting, user agents
2104 may approximate font sizes, for example to align baselines. Also, the
2105 glyph outline may be taken into account when formatting.</p>
2106
2107 <p>Punctuation (i.e, characters defined in Unicode in the "open" (Ps),
2108 "close" (Pe), "initial" (Pi). "final" (Pf) and "other" (Po)
2109 punctuation classes), that precedes or follows the first letter should
2110 be included. <a href="#refsUNICODE">[UNICODE]</a></p>
2111
2112 <div class="figure">
2113 <P><img src="first-letter2.gif" alt="Quotes that precede the
2114 first letter should be included."></p>
2115 </div>
2116
2117 <p>The <code>::first-letter</code> also applies if the first letter is
2118 in fact a digit, e.g., the "6" in "67 million dollars is a lot of
2119 money."</p>
2120
2121 <p>In CSS, the <code>::first-letter</code> pseudo-element applies to
2122 block, list-item, table-cell, table-caption, and inline-block
2123 elements. <span class="note">A future version of this specification
2124 may allow this pesudo-element to apply to more element
2125 types.</span></p>
2126
2127 <p>The <code>::first-letter</code> pseudo-element can be used with all
2128 such elements that contain text, or that have a descendant in the same
2129 flow that contains text. A UA should act as if the fictional start tag
2130 of the ::first-letter pseudo-element is just before the first text of
2131 the element, even if that first text is in a descendant.</p>
2132
2133 <div class="example">
2134 <p>Example:</p>
2135 <p>The fictional tag sequence for this HTMLfragment:
2136 <pre>&lt;div>
2137 &lt;p>The first text.</pre>
2138 <p>is:
2139 <pre>&lt;div>
2140 &lt;p>&lt;div::first-letter>&lt;p::first-letter>T&lt;/...>&lt;/...>he first text .</pre>
2141 </div>
2142
2143 <p>The first letter of a table-cell or inline-block cannot be the
2144 first letter of an ancestor element. Thus, in <code>&lt;DIV&gt;&lt;P
2145 STYLE="display: inline-block">Hello&lt;BR&gt;Goodbye&lt;/P&gt;
2146 etcetera&lt;/DIV&gt;</code> the first letter of the <code>div</code> is not the
2147 letter "H". In fact, the <code>div</code> doesn't have a first letter.
2148
2149 <p>The first letter must occur on the <a
2150 href="#first-formatted-line">first formatted line.</a> For example, in
2151 this fragment: <code>&lt;p&gt&lt;br&gt;First...</code> the first line
2152 doesn't contain any letters and <code>::first-letter</code> doesn't
2153 match anything (assuming the default style for <code>br</code> in HTML
2154 4). In particular, it does not match the "F" of "First."
2155
2156 <p>In CSS, if an element is a list item ('display: list-item'), the
2157 <code>::first-letter</code> applies to the first letter in the
2158 principal box after the marker. UAs may ignore
2159 <code>::first-letter</code> on list items with 'list-style-position:
2160 inside'. If an element has <code>::before</code> or
2161 <code>::after</code> content, the <code>::first-letter</code> applies
2162 to the first letter of the element <em>including</em> that content.
2163
2164 <div class="example">
2165 <p>Example:</p>
2166 <p>After the rule 'p::before {content: "Note: "}', the selector
2167 'p::first-letter' matches the "N" of "Note".</p>
2168 </div>
2169
2170 <p>Some languages may have specific rules about how to treat certain
2171 letter combinations. In Dutch, for example, if the letter combination
2172 "ij" appears at the beginning of a word, both letters should be
2173 considered within the <code>::first-letter</code> pseudo-element.
2174
2175 <p>If the letters that would form the ::first-letter are not in the
2176 same element, such as "'T" in <code>&lt;p>'&lt;em>T...</code>, the UA
2177 may create a ::first-letter pseudo-element from one of the elements,
2178 both elements, or simply not create a pseudo-element.</p>
2179
2180 <p>Similarly, if the first letter(s) of the block are not at the start
2181 of the line (for example due to bidirectional reordering), then the UA
2182 need not create the pseudo-element(s).
2183
2184 <div class="example">
2185 <p>Example:</p>
2186 <p><a name="overlapping-example">The following example</a> illustrates
2187 how overlapping pseudo-elements may interact. The first letter of
2188 each P element will be green with a font size of '24pt'. The rest of
2189 the first formatted line will be 'blue' while the rest of the
2190 paragraph will be 'red'.</p>
2191
2192 <pre>p { color: red; font-size: 12pt }
2193 p::first-letter { color: green; font-size: 200% }
2194 p::first-line { color: blue }
2195
2196 &lt;P&gt;Some text that ends up on two lines&lt;/P&gt;</pre>
2197
2198 <p>Assuming that a line break will occur before the word "ends", the
2199 <span class="index-inst" title="fictional tag sequence">fictional tag
2200 sequence</span> for this fragment might be:</p>
2201
2202 <pre>&lt;P&gt;
2203 &lt;P::first-line&gt;
2204 &lt;P::first-letter&gt;
2205 S
2206 &lt;/P::first-letter&gt;ome text that
2207 &lt;/P::first-line&gt;
2208 ends up on two lines
2209 &lt;/P&gt;</pre>
2210
2211 <p>Note that the <code>::first-letter</code> element is inside the <code>::first -line</code>
2212 element. Properties set on <code>::first-line</code> are inherited by
2213 <code>::first-letter</code>, but are overridden if the same property is set on
2214 <code>::first-letter</code>.</p>
2215 </div>
2216
2217
2218 <h4><a name=UIfragments>7.3.</a> <a name=selection>The ::selection pseudo-elemen t</a></h4>
2219
2220 <p>The <code>::selection</code> pseudo-element applies to the portion
2221 of a document that has been highlighted by the user. This also
2222 applies, for example, to selected text within an editable text
2223 field. This pseudo-element should not be confused with the <code><a
2224 href="#checked">:checked</a></code> pseudo-class (which used to be
2225 named <code>:selected</code>)
2226
2227 <p>Although the <code>::selection</code> pseudo-element is dynamic in
2228 nature, and is altered by user action, it is reasonable to expect that
2229 when a UA re-renders to a static medium (such as a printed page, see
2230 <a href="#refsCSS21">[CSS21]</a>) which was originally rendered to a
2231 dynamic medium (like screen), the UA may wish to transfer the current
2232 <code>::selection</code> state to that other medium, and have all the
2233 appropriate formatting and rendering take effect as well. This is not
2234 required &mdash; UAs may omit the <code>::selection</code>
2235 pseudo-element for static media.
2236
2237 <p>These are the CSS properties that apply to <code>::selection</code>
2238 pseudo-elements: color, background, cursor (optional), outline
2239 (optional). The computed value of the 'background-image' property on
2240 <code>::selection</code> may be ignored.
2241
2242
2243 <h4><a name=gen-content>7.4. The ::before and ::after pseudo-elements</a></h4>
2244
2245 <p>The <code>::before</code> and <code>::after</code> pseudo-elements
2246 can be used to describe generated content before or after an element's
2247 content. They are explained in CSS 2.1 <a
2248 href="#refsCSS21">[CSS21]</a>.</p>
2249
2250 <p>When the <code>::first-letter</code> and <code>::first-line</code>
2251 pseudo-elements are combined with <code>::before</code> and
2252 <code>::after</code>, they apply to the first letter or line of the
2253 element including the inserted text.</p>
2254
2255 <h2><a name=combinators>8. Combinators</a></h2>
2256
2257 <h3><a name=descendant-combinators>8.1. Descendant combinator</a></h3>
2258
2259 <p>At times, authors may want selectors to describe an element that is
2260 the descendant of another element in the document tree (e.g., "an
2261 <code>EM</code> element that is contained within an <code>H1</code>
2262 element"). Descendant combinators express such a relationship. A
2263 descendant combinator is <a href="#whitespace">white space</a> that
2264 separates two sequences of simple selectors. A selector of the form
2265 "<code>A B</code>" represents an element <code>B</code> that is an
2266 arbitrary descendant of some ancestor element <code>A</code>.
2267
2268 <div class="example">
2269 <p>Examples:</p>
2270 <p>For example, consider the following selector:</p>
2271 <pre>h1 em</pre>
2272 <p>It represents an <code>em</code> element being the descendant of
2273 an <code>h1</code> element. It is a correct and valid, but partial,
2274 description of the following fragment:</p>
2275 <pre>&lt;h1&gt;This &lt;span class="myclass"&gt;headline
2276 is &lt;em&gt;very&lt;/em&gt; important&lt;/span&gt;&lt;/h1&gt;</pre>
2277 <p>The following selector:</p>
2278 <pre>div * p</pre>
2279 <p>represents a <code>p</code> element that is a grandchild or later
2280 descendant of a <code>div</code> element. Note the whitespace on
2281 either side of the "*" is not part of the universal selector; the
2282 whitespace is a combinator indicating that the DIV must be the
2283 ancestor of some element, and that that element must be an ancestor
2284 of the P.</p>
2285 <p>The following selector, which combines descendant combinators and
2286 <a href="#attribute-selectors">attribute selectors</a>, represents an
2287 element that (1) has the <code>href</code> attribute set and (2) is
2288 inside a <code>p</code> that is itself inside a <code>div</code>:</p>
2289 <pre>div p *[href]</pre>
2290 </div>
2291
2292 <h3><a name=child-combinators>8.2. Child combinators</a></h3>
2293
2294 <p>A <dfn>child combinator</dfn> describes a childhood relationship
2295 between two elements. A child combinator is made of the
2296 &quot;greater-than sign&quot; (<code>&gt;</code>) character and
2297 separates two sequences of simple selectors.
2298
2299
2300 <div class="example">
2301 <p>Examples:</p>
2302 <p>The following selector represents a <code>p</code> element that is
2303 child of <code>body</code>:</p>
2304 <pre>body &gt; p</pre>
2305 <p>The following example combines descendant combinators and child
2306 combinators.</p>
2307 <pre>div ol&gt;li p</pre><!-- LEAVE THOSE SPACES OUT! see below -->
2308 <p>It represents a <code>p</code> element that is a descendant of an
2309 <code>li</code> element; the <code>li</code> element must be the
2310 child of an <code>ol</code> element; the <code>ol</code> element must
2311 be a descendant of a <code>div</code>. Notice that the optional white
2312 space around the "&gt;" combinator has been left out.</p>
2313 </div>
2314
2315 <p>For information on selecting the first child of an element, please
2316 see the section on the <code><a
2317 href="#structural-pseudos">:first-child</a></code> pseudo-class
2318 above.</p>
2319
2320 <h3><a name=sibling-combinators>8.3. Sibling combinators</a></h3>
2321
2322 <p>There are two different sibling combinators: the adjacent sibling
2323 combinator and the general sibling combinator. In both cases,
2324 non-element nodes (e.g. text between elements) are ignored when
2325 considering adjacency of elements.</p>
2326
2327 <h4><a name=adjacent-sibling-combinators>8.3.1. Adjacent sibling combinator</a>< /h4>
2328
2329 <p>The adjacent sibling combinator is made of the &quot;plus
2330 sign&quot; (U+002B, <code>+</code>) character that separates two
2331 sequences of simple selectors. The elements represented by the two
2332 sequences share the same parent in the document tree and the element
2333 represented by the first sequence immediately precedes the element
2334 represented by the second one.</p>
2335
2336 <div class="example">
2337 <p>Examples:</p>
2338 <p>The following selector represents a <code>p</code> element
2339 immediately following a <code>math</code> element:</p>
2340 <pre>math + p</pre>
2341 <p>The following selector is conceptually similar to the one in the
2342 previous example, except that it adds an attribute selector &mdash; it
2343 adds a constraint to the <code>h1</code> element, that it must have
2344 <code>class="opener"</code>:</p>
2345 <pre>h1.opener + h2</pre>
2346 </div>
2347
2348
2349 <h4><a name=general-sibling-combinators>8.3.2. General sibling combinator</a></h 4>
2350
2351 <p>The general sibling combinator is made of the &quot;tilde&quot;
2352 (U+007E, <code>~</code>) character that separates two sequences of
2353 simple selectors. The elements represented by the two sequences share
2354 the same parent in the document tree and the element represented by
2355 the first sequence precedes (not necessarily immediately) the element
2356 represented by the second one.</p>
2357
2358 <div class="example">
2359 <p>Example:</p>
2360 <pre>h1 ~ pre</pre>
2361 <p>represents a <code>pre</code> element following an <code>h1</code>. It
2362 is a correct and valid, but partial, description of:</p>
2363 <pre>&lt;h1&gt;Definition of the function a&lt;/h1&gt;
2364 &lt;p&gt;Function a(x) has to be applied to all figures in the table.&lt;/p&gt;
2365 &lt;pre&gt;function a(x) = 12x/13.5&lt;/pre&gt;</pre>
2366 </div>
2367
2368 <h2><a name=specificity>9. Calculating a selector's specificity</a></h2>
2369
2370 <p>A selector's specificity is calculated as follows:</p>
2371
2372 <ul>
2373 <li>count the number of ID selectors in the selector (= a)</li>
2374 <li>count the number of class selectors, attributes selectors, and pseudo-clas ses in the selector (= b)</li>
2375 <li>count the number of element names in the selector (= c)</li>
2376 <li>ignore pseudo-elements</li>
2377 </ul>
2378
2379 <p>Selectors inside <a href="#negation">the negation pseudo-class</a>
2380 are counted like any other, but the negation itself does not count as
2381 a pseudo-class.</p>
2382
2383 <p>Concatenating the three numbers a-b-c (in a number system with a
2384 large base) gives the specificity.</p>
2385
2386 <div class="example">
2387 <p>Examples:</p>
2388 <pre>* /* a=0 b=0 c=0 -&gt; specificity = 0 */
2389 LI /* a=0 b=0 c=1 -&gt; specificity = 1 */
2390 UL LI /* a=0 b=0 c=2 -&gt; specificity = 2 */
2391 UL OL+LI /* a=0 b=0 c=3 -&gt; specificity = 3 */
2392 H1 + *[REL=up] /* a=0 b=1 c=1 -&gt; specificity = 11 */
2393 UL OL LI.red /* a=0 b=1 c=3 -&gt; specificity = 13 */
2394 LI.red.level /* a=0 b=2 c=1 -&gt; specificity = 21 */
2395 #x34y /* a=1 b=0 c=0 -&gt; specificity = 100 */
2396 #s12:not(FOO) /* a=1 b=0 c=1 -&gt; specificity = 101 */
2397 </pre>
2398 </div>
2399
2400 <p class="note"><strong>Note:</strong> the specificity of the styles
2401 specified in an HTML <code>style</code> attribute is described in CSS
2402 2.1. <a href="#refsCSS21">[CSS21]</a>.</p>
2403
2404 <h2><a name=w3cselgrammar>10. The grammar of Selectors</a></h2>
2405
2406 <h3><a name=grammar>10.1. Grammar</a></h3>
2407
2408 <p>The grammar below defines the syntax of Selectors. It is globally
2409 LL(1) and can be locally LL(2) (but note that most UA's should not use
2410 it directly, since it doesn't express the parsing conventions). The
2411 format of the productions is optimized for human consumption and some
2412 shorthand notations beyond Yacc (see <a href="#refsYACC">[YACC]</a>)
2413 are used:</p>
2414
2415 <ul>
2416 <li><b>*</b>: 0 or more
2417 <li><b>+</b>: 1 or more
2418 <li><b>?</b>: 0 or 1
2419 <li><b>|</b>: separates alternatives
2420 <li><b>[ ]</b>: grouping </li>
2421 </ul>
2422
2423 <p>The productions are:</p>
2424
2425 <pre>selectors_group
2426 : selector [ COMMA S* selector ]*
2427 ;
2428
2429 selector
2430 : simple_selector_sequence [ combinator simple_selector_sequence ]*
2431 ;
2432
2433 combinator
2434 /* combinators can be surrounded by white space */
2435 : PLUS S* | GREATER S* | TILDE S* | S+
2436 ;
2437
2438 simple_selector_sequence
2439 : [ type_selector | universal ]
2440 [ HASH | class | attrib | pseudo | negation ]*
2441 | [ HASH | class | attrib | pseudo | negation ]+
2442 ;
2443
2444 type_selector
2445 : [ namespace_prefix ]? element_name
2446 ;
2447
2448 namespace_prefix
2449 : [ IDENT | '*' ]? '|'
2450 ;
2451
2452 element_name
2453 : IDENT
2454 ;
2455
2456 universal
2457 : [ namespace_prefix ]? '*'
2458 ;
2459
2460 class
2461 : '.' IDENT
2462 ;
2463
2464 attrib
2465 : '[' S* [ namespace_prefix ]? IDENT S*
2466 [ [ PREFIXMATCH |
2467 SUFFIXMATCH |
2468 SUBSTRINGMATCH |
2469 '=' |
2470 INCLUDES |
2471 DASHMATCH ] S* [ IDENT | STRING ] S*
2472 ]? ']'
2473 ;
2474
2475 pseudo
2476 /* '::' starts a pseudo-element, ':' a pseudo-class */
2477 /* Exceptions: :first-line, :first-letter, :before and :after. */
2478 /* Note that pseudo-elements are restricted to one per selector and */
2479 /* occur only in the last simple_selector_sequence. */
2480 : ':' ':'? [ IDENT | functional_pseudo ]
2481 ;
2482
2483 functional_pseudo
2484 : FUNCTION S* expression ')'
2485 ;
2486
2487 expression
2488 /* In CSS3, the expressions are identifiers, strings, */
2489 /* or of the form "an+b" */
2490 : [ [ PLUS | '-' | DIMENSION | NUMBER | STRING | IDENT ] S* ]+
2491 ;
2492
2493 negation
2494 : NOT S* negation_arg S* ')'
2495 ;
2496
2497 negation_arg
2498 : type_selector | universal | HASH | class | attrib | pseudo
2499 ;</pre>
2500
2501
2502 <h3><a name=lex>10.2. Lexical scanner</a></h3>
2503
2504 <p>The following is the <a name=x3>tokenizer</a>, written in Flex (see
2505 <a href="#refsFLEX">[FLEX]</a>) notation. The tokenizer is
2506 case-insensitive.</p>
2507
2508 <p>The two occurrences of "\377" represent the highest character
2509 number that current versions of Flex can deal with (decimal 255). They
2510 should be read as "\4177777" (decimal 1114111), which is the highest
2511 possible code point in Unicode/ISO-10646. <a
2512 href="#refsUNICODE">[UNICODE]</a></p>
2513
2514 <pre>%option case-insensitive
2515
2516 ident [-]?{nmstart}{nmchar}*
2517 name {nmchar}+
2518 nmstart [_a-z]|{nonascii}|{escape}
2519 nonascii [^\0-\177]
2520 unicode \\[0-9a-f]{1,6}(\r\n|[ \n\r\t\f])?
2521 escape {unicode}|\\[^\n\r\f0-9a-f]
2522 nmchar [_a-z0-9-]|{nonascii}|{escape}
2523 num [0-9]+|[0-9]*\.[0-9]+
2524 string {string1}|{string2}
2525 string1 \"([^\n\r\f\\"]|\\{nl}|{nonascii}|{escape})*\"
2526 string2 \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*\'
2527 invalid {invalid1}|{invalid2}
2528 invalid1 \"([^\n\r\f\\"]|\\{nl}|{nonascii}|{escape})*
2529 invalid2 \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*
2530 nl \n|\r\n|\r|\f
2531 w [ \t\r\n\f]*
2532
2533 %%
2534
2535 [ \t\r\n\f]+ return S;
2536
2537 "~=" return INCLUDES;
2538 "|=" return DASHMATCH;
2539 "^=" return PREFIXMATCH;
2540 "$=" return SUFFIXMATCH;
2541 "*=" return SUBSTRINGMATCH;
2542 {ident} return IDENT;
2543 {string} return STRING;
2544 {ident}"(" return FUNCTION;
2545 {num} return NUMBER;
2546 "#"{name} return HASH;
2547 {w}"+" return PLUS;
2548 {w}"&gt;" return GREATER;
2549 {w}"," return COMMA;
2550 {w}"~" return TILDE;
2551 ":not(" return NOT;
2552 @{ident} return ATKEYWORD;
2553 {invalid} return INVALID;
2554 {num}% return PERCENTAGE;
2555 {num}{ident} return DIMENSION;
2556 "&lt;!--" return CDO;
2557 "--&gt;" return CDC;
2558
2559 "url("{w}{string}{w}")" return URI;
2560 "url("{w}([!#$%&*-~]|{nonascii}|{escape})*{w}")" return URI;
2561 U\+[0-9a-f?]{1,6}(-[0-9a-f]{1,6})? return UNICODE_RANGE;
2562
2563 \/\*[^*]*\*+([^/*][^*]*\*+)*\/ /* ignore comments */
2564
2565 . return *yytext;</pre>
2566
2567
2568
2569 <h2><a name=downlevel>11. Namespaces and down-level clients</a></h2>
2570
2571 <p>An important issue is the interaction of CSS selectors with XML
2572 documents in web clients that were produced prior to this
2573 document. Unfortunately, due to the fact that namespaces must be
2574 matched based on the URI which identifies the namespace, not the
2575 namespace prefix, some mechanism is required to identify namespaces in
2576 CSS by their URI as well. Without such a mechanism, it is impossible
2577 to construct a CSS style sheet which will properly match selectors in
2578 all cases against a random set of XML documents. However, given
2579 complete knowledge of the XML document to which a style sheet is to be
2580 applied, and a limited use of namespaces within the XML document, it
2581 is possible to construct a style sheet in which selectors would match
2582 elements and attributes correctly.</p>
2583
2584 <p>It should be noted that a down-level CSS client will (if it
2585 properly conforms to CSS forward compatible parsing rules) ignore all
2586 <code>@namespace</code> at-rules, as well as all style rules that make
2587 use of namespace qualified element type or attribute selectors. The
2588 syntax of delimiting namespace prefixes in CSS was deliberately chosen
2589 so that down-level CSS clients would ignore the style rules rather
2590 than possibly match them incorrectly.</p>
2591
2592 <p>The use of default namespaces in CSS makes it possible to write
2593 element type selectors that will function in both namespace aware CSS
2594 clients as well as down-level clients. It should be noted that
2595 down-level clients may incorrectly match selectors against XML
2596 elements in other namespaces.</p>
2597
2598 <p>The following are scenarios and examples in which it is possible to
2599 construct style sheets which would function properly in web clients
2600 that do not implement this proposal.</p>
2601
2602 <ol>
2603 <li>
2604
2605 <p>The XML document does not use namespaces.</p>
2606
2607 <ul>
2608
2609 <li>In this case, it is obviously not necessary to declare or use
2610 namespaces in the style sheet. Standard CSS element type and
2611 attribute selectors will function adequately in a down-level
2612 client.</li>
2613
2614 <li>In a CSS namespace aware client, the default behavior of
2615 element selectors matching without regard to namespace will
2616 function properly against all elements, since no namespaces are
2617 present. However, the use of specific element type selectors that
2618 match only elements that have no namespace ("<code>|name</code>")
2619 will guarantee that selectors will match only XML elements that do
2620 not have a declared namespace. </li>
2621
2622 </ul>
2623
2624 </li>
2625
2626 <li>
2627
2628 <p>The XML document defines a single, default namespace used
2629 throughout the document. No namespace prefixes are used in element
2630 names.</p>
2631
2632 <ul>
2633
2634 <li>In this case, a down-level client will function as if
2635 namespaces were not used in the XML document at all. Standard CSS
2636 element type and attribute selectors will match against all
2637 elements. </li>
2638
2639 </ul>
2640
2641 </li>
2642
2643 <li>
2644
2645 <p>The XML document does <b>not</b> use a default namespace, all
2646 namespace prefixes used are known to the style sheet author, and
2647 there is a direct mapping between namespace prefixes and namespace
2648 URIs. (A given prefix may only be mapped to one namespace URI
2649 throughout the XML document; there may be multiple prefixes mapped
2650 to the same URI).</p>
2651
2652 <ul>
2653
2654 <li>In this case, the down-level client will view and match
2655 element type and attribute selectors based on their fully
2656 qualified name, not the local part as outlined in the <a
2657 href="#typenmsp">Type selectors and Namespaces</a> section. CSS
2658 selectors may be declared using an escaped colon "<code>\:</code>"
2659 to describe the fully qualified names, e.g.
2660 "<code>html\:h1</code>" will match
2661 <code>&lt;html:h1&gt;</code>. Selectors using the qualified name
2662 will only match XML elements that use the same prefix. Other
2663 namespace prefixes used in the XML that are mapped to the same URI
2664 will not match as expected unless additional CSS style rules are
2665 declared for them.</li>
2666
2667 <li>Note that selectors declared in this fashion will
2668 <em>only</em> match in down-level clients. A CSS namespace aware
2669 client will match element type and attribute selectors based on
2670 the name's local part. Selectors declared with the fully
2671 qualified name will not match (unless there is no namespace prefix
2672 in the fully qualified name).</li>
2673
2674 </ul>
2675
2676 </li>
2677
2678 </ol>
2679
2680 <p>In other scenarios: when the namespace prefixes used in the XML are
2681 not known in advance by the style sheet author; or a combination of
2682 elements with no namespace are used in conjunction with elements using
2683 a default namespace; or the same namespace prefix is mapped to
2684 <em>different</em> namespace URIs within the same document, or in
2685 different documents; it is impossible to construct a CSS style sheet
2686 that will function properly against all elements in those documents,
2687 unless, the style sheet is written using a namespace URI syntax (as
2688 outlined in this document or similar) and the document is processed by
2689 a CSS and XML namespace aware client.</p>
2690
2691 <h2><a name=profiling>12. Profiles</a></h2>
2692
2693 <p>Each specification using Selectors must define the subset of W3C
2694 Selectors it allows and excludes, and describe the local meaning of
2695 all the components of that subset.</p>
2696
2697 <p>Non normative examples:
2698
2699 <div class="profile">
2700 <table class="tprofile">
2701 <tbody>
2702 <tr>
2703 <th class="title" colspan=2>Selectors profile</th></tr>
2704 <tr>
2705 <th>Specification</th>
2706 <td>CSS level 1</td></tr>
2707 <tr>
2708 <th>Accepts</th>
2709 <td>type selectors<br>class selectors<br>ID selectors<br>:link,
2710 :visited and :active pseudo-classes<br>descendant combinator
2711 <br>::first-line and ::first-letter pseudo-elements</td></tr>
2712 <tr>
2713 <th>Excludes</th>
2714 <td>
2715
2716 <p>universal selector<br>attribute selectors<br>:hover and :focus
2717 pseudo-classes<br>:target pseudo-class<br>:lang() pseudo-class<br>all UI
2718 element states pseudo-classes<br>all structural
2719 pseudo-classes<br>negation pseudo-class<br>all
2720 UI element fragments pseudo-elements<br>::before and ::after
2721 pseudo-elements<br>child combinators<br>sibling combinators
2722
2723 <p>namespaces</td></tr>
2724 <tr>
2725 <th>Extra constraints</th>
2726 <td>only one class selector allowed per sequence of simple
2727 selectors</td></tr></tbody></table><br><br>
2728 <table class="tprofile">
2729 <tbody>
2730 <tr>
2731 <th class="title" colspan=2>Selectors profile</th></tr>
2732 <tr>
2733 <th>Specification</th>
2734 <td>CSS level 2</td></tr>
2735 <tr>
2736 <th>Accepts</th>
2737 <td>type selectors<br>universal selector<br>attribute presence and
2738 values selectors<br>class selectors<br>ID selectors<br>:link, :visited,
2739 :active, :hover, :focus, :lang() and :first-child pseudo-classes
2740 <br>descendant combinator<br>child combinator<br>adjacent sibling
2741 combinator<br>::first-line and ::first-letter pseudo-elements<br>::before
2742 and ::after pseudo-elements</td></tr>
2743 <tr>
2744 <th>Excludes</th>
2745 <td>
2746
2747 <p>content selectors<br>substring matching attribute
2748 selectors<br>:target pseudo-classes<br>all UI element
2749 states pseudo-classes<br>all structural pseudo-classes other
2750 than :first-child<br>negation pseudo-class<br>all UI element
2751 fragments pseudo-elements<br>general sibling combinators
2752
2753 <p>namespaces</td></tr>
2754 <tr>
2755 <th>Extra constraints</th>
2756 <td>more than one class selector per sequence of simple selectors (CSS1
2757 constraint) allowed</td></tr></tbody></table>
2758
2759 <p>In CSS, selectors express pattern matching rules that determine which style
2760 rules apply to elements in the document tree.
2761
2762 <p>The following selector (CSS level 2) will <b>match</b> all anchors <code>a</c ode>
2763 with attribute <code>name</code> set inside a section 1 header <code>h1</code>:
2764 <pre>h1 a[name]</pre>
2765
2766 <p>All CSS declarations attached to such a selector are applied to elements
2767 matching it. </div>
2768
2769 <div class="profile">
2770 <table class="tprofile">
2771 <tbody>
2772 <tr>
2773 <th class="title" colspan=2>Selectors profile</th></tr>
2774 <tr>
2775 <th>Specification</th>
2776 <td>STTS 3</td>
2777 </tr>
2778 <tr>
2779 <th>Accepts</th>
2780 <td>
2781
2782 <p>type selectors<br>universal selectors<br>attribute selectors<br>class
2783 selectors<br>ID selectors<br>all structural pseudo-classes<br>
2784 all combinators
2785
2786 <p>namespaces</td></tr>
2787 <tr>
2788 <th>Excludes</th>
2789 <td>non-accepted pseudo-classes<br>pseudo-elements<br></td></tr>
2790 <tr>
2791 <th>Extra constraints</th>
2792 <td>some selectors and combinators are not allowed in fragment
2793 descriptions on the right side of STTS declarations.</td></tr></tbody></ta ble>
2794 <form>
2795 <input type="text" name="test1"/>
2796 <input type="text" name="foo"/>
2797 <input type="text" name="foo"/>
2798 <input type="text" name="foo"/>
2799 <input type="text" name="foo"/>
2800 <input type="text" name="foo"/>
2801 <input type="text" name="foo"/>
2802 <input type="text" name="foo"/>
2803 <input type="text" name="foo"/>
2804 <input type="text" name="foo"/>
2805 <input type="text" name="foo"/>
2806 <input type="text" name="foo"/>
2807 <input type="text" name="foo"/>
2808 <input type="text" name="foo"/>
2809 <input type="text" name="foo"/>
2810 <input type="text" name="foo"/>
2811 <input type="text" name="foo"/>
2812 <input type="text" name="foo"/>
2813 <input type="text" name="foo"/>
2814 <input type="text" name="foo"/>
2815 <input type="text" name="foo"/>
2816 <input type="text" name="foo"/>
2817 <input type="text" name="foo"/>
2818 <input type="text" name="foo"/>
2819 <input type="text" name="foo"/>
2820 </form>
2821
2822 <p>Selectors can be used in STTS 3 in two different
2823 manners:
2824 <ol>
2825 <li>a selection mechanism equivalent to CSS selection mechanism: declarations
2826 attached to a given selector are applied to elements matching that selector,
2827 <li>fragment descriptions that appear on the right side of declarations.
2828 </li></ol></div>
2829
2830 <h2><a name=Conformance></a>13. Conformance and requirements</h2>
2831
2832 <p>This section defines conformance with the present specification only.
2833
2834 <p>The inability of a user agent to implement part of this specification due to
2835 the limitations of a particular device (e.g., non interactive user agents will
2836 probably not implement dynamic pseudo-classes because they make no sense without
2837 interactivity) does not imply non-conformance.
2838
2839 <p>All specifications reusing Selectors must contain a <a
2840 href="#profiling">Profile</a> listing the
2841 subset of Selectors it accepts or excludes, and describing the constraints
2842 it adds to the current specification.
2843
2844 <p>Invalidity is caused by a parsing error, e.g. an unrecognized token or a toke n
2845 which is not allowed at the current parsing point.
2846
2847 <p>User agents must observe the rules for handling parsing errors:
2848 <ul>
2849 <li>a simple selector containing an undeclared namespace prefix is invalid</li >
2850 <li>a selector containing an invalid simple selector, an invalid combinator
2851 or an invalid token is invalid. </li>
2852 <li>a group of selectors containing an invalid selector is invalid.</li>
2853 </ul>
2854
2855 <p class="foo test1 bar">Specifications reusing Selectors must define how to han dle parsing
2856 errors. (In the case of CSS, the entire rule in which the selector is
2857 used is dropped.)</p>
2858
2859 <!-- Apparently all these references are out of date:
2860 <p>Implementations of this specification must behave as
2861 "recipients of text data" as defined by <a href="#refsCWWW">[CWWW]</a>
2862 when parsing selectors and attempting matches. (In particular,
2863 implementations must assume the data is normalized and must not
2864 normalize it.) Normative rules for matching strings are defined in
2865 <a href="#refsCWWW">[CWWW]</a> and <a
2866 href="#refsUNICODE">[UNICODE]</a> and apply to implementations of this
2867 specification.</p>-->
2868
2869 <h2><a name=Tests></a>14. Tests</h2>
2870
2871 <p>This specification has <a
2872 href="http://www.w3.org/Style/CSS/Test/CSS3/Selectors/current/">a test
2873 suite</a> allowing user agents to verify their basic conformance to
2874 the specification. This test suite does not pretend to be exhaustive
2875 and does not cover all possible combined cases of Selectors.</p>
2876
2877 <h2><a name=ACKS></a>15. Acknowledgements</h2>
2878
2879 <p>The CSS working group would like to thank everyone who has sent
2880 comments on this specification over the years.</p>
2881
2882 <p>The working group would like to extend special thanks to Donna
2883 McManus, Justin Baker, Joel Sklar, and Molly Ives Brower who perfermed
2884 the final editorial review.</p>
2885
2886 <h2><a name=references>16. References</a></h2>
2887
2888 <dl class="refs">
2889
2890 <dt>[CSS1]
2891 <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
2892 <dd>(<code><a href="http://www.w3.org/TR/REC-CSS1">http://www.w3.org/TR/REC-CS S1</a></code>)
2893
2894 <dt>[CSS21]
2895 <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
2896 <dd>(<code><a href="http://www.w3.org/TR/CSS21">http://www.w3.org/TR/CSS21</a> </code>)
2897
2898 <dt>[CWWW]
2899 <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
2900 <dd>(<code><a href="http://www.w3.org/TR/charmod/">http://www.w3.org/TR/charmo d/</a></code>)
2901
2902 <dt>[FLEX]
2903 <dd><a name="refsFLEX"></a> "<cite>Flex: The Lexical Scanner Generator</cite>" , Version 2.3.7, ISBN 1882114213
2904
2905 <dt>[HTML4]
2906 <dd><a name="refsHTML4"></a> Dave Ragget, Arnaud Le Hors, Ian Jacobs, editors; "<cite>HTML 4.01 Specification</cite>", W3C Recommendation, 24 December 1999
2907 <dd>(<a href="http://www.w3.org/TR/html4/"><code>http://www.w3.org/TR/html4/</ code></a>)
2908
2909 <dt>[MATH]
2910 <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
2911 <dd>(<code><a href="http://www.w3.org/TR/REC-MathML/">http://www.w3.org/TR/REC -MathML/</a></code>)
2912
2913 <dt>[RFC3066]
2914 <dd><a name="refsRFC3066"></a> H. Alvestrand; "<cite>Tags for the Identificati on of Languages</cite>", Request for Comments 3066, January 2001
2915 <dd>(<a href="http://www.ietf.org/rfc/rfc3066.txt"><code>http://www.ietf.org/r fc/rfc3066.txt</code></a>)
2916
2917 <dt>[STTS]
2918 <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
2919 <dd>(<code><a href="http://www.w3.org/TR/NOTE-STTS3">http://www.w3.org/TR/NOTE -STTS3</a></code>)
2920
2921 <dt>[SVG]
2922 <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
2923 <dd>(<code><a href="http://www.w3.org/TR/SVG/">http://www.w3.org/TR/SVG/</a></ code>)
2924
2925 <dt>[UNICODE]</dt>
2926 <dd><a name="refsUNICODE"></a> <cite><a
2927 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>.
2928 <dd>(<code><a href="http://www.unicode.org/versions/">http://www.unicode.org/v ersions/</a></code>)</dd>
2929
2930 <dt>[XML10]
2931 <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
2932 <dd>(<a href="http://www.w3.org/TR/REC-xml/"><code>http://www.w3.org/TR/REC-xm l/</code></a>)
2933
2934 <dt>[XMLNAMES]
2935 <dd><a name="refsXMLNAMES"></a> Tim Bray, Dave Hollander, Andrew Layman, edito rs; "<cite>Namespaces in XML</cite>", W3C Recommendation, 14 January 1999
2936 <dd>(<a href="http://www.w3.org/TR/REC-xml-names/"><code>http://www.w3.org/TR/ REC-xml-names/</code></a>)
2937
2938 <dt>[YACC]
2939 <dd><a name="refsYACC"></a> S. C. Johnson; "<cite>YACC &mdash; Yet another com piler compiler</cite>", Technical Report, Murray Hill, 1975
2940
2941 </dl>
2942 </body>
2943 </html>
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