Return 404s for unknown URLs. Also scroll back to the top of the page upon following a link.

doc/templates/index.html

Index: doc/templates/index.html
diff --git a/doc/templates/index.html b/doc/templates/index.html
index e78bd849921bfb2176b4f827a19f9a646cdabd15..23c0e3969be3831449a4e5826613c5fdd4e8a531 100644
--- a/doc/templates/index.html
+++ b/doc/templates/index.html
@@ -87,6 +87,7 @@
               window.history.pushState(null, null, url);
               highlightNav();
               $$$('html #content').innerHTML = content;
+              $$$('html #page').scrollIntoView();
               prettyPrint();
             });
             e.preventDefault();