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170 <body>
172 <p><a href="http://www.w3.org/"><img height=48 alt=W3C src="http://www.w3.org/Icons/w3c_home" width=72></a>
178 <dl>
180 <dt>This version:
185 <dt>Latest version:
188 http://www.w3.org/TR/css3-selectors</a>
190 <dt>Previous version:
199 <dd class="vcard"><a lang="tr" class="url fn" href="http://www.tantek.com/">Tantek Çelik</a> (Invited Expert)
207 <dd class="vcard"><span class="fn">John Williams</span> (former editor, <span class="company"><a
210 </dl>
221 <a
223 <a
225 <a
227 use</a> rules apply.
231 </div>
236 tree. Selectors have been optimized for use with HTML and XML, and
237 are designed to be usable in performance-critical code.</p>
240 Style Sheets) is a language for describing the rendering of <acronym
243 screen, on paper, in speech, etc. CSS uses Selectors for binding
244 style properties to elements in the document. This document
245 describes extensions to the selectors defined in CSS level 2. These
246 extended selectors will be used by CSS level 3.
252 <p>That is, given an element and a selector, this specification
253 defines whether that element matches the selector.</p>
255 <p>These expressions can also be used, for instance, to select a set
256 of elements, or a single element from a set of elements, by
257 evaluating the expression across all the elements in a
264 <p><em>This section describes the status of this document at the
265 time of its publication. Other documents may supersede this
266 document. A list of current W3C publications and the latest revision
267 of this technical report can be found in the <a
269 http://www.w3.org/TR/.</a></em></p>
277 <p>The CSS Working Group doesn't expect that all implementations of
278 CSS3 will have to implement all selectors. Instead, there will
279 probably be a small number of variants of CSS3, called profiles. For
280 example, it may be that only a profile for interactive user agents
281 will include all of the selectors.</p>
286 document is a revision of the <a
289 implementation feedback received in the past few years. It is
290 expected that this last call will proceed straight to Proposed
291 Recommendation stage since it is believed that interoperability will
292 be demonstrable.</p>
294 <p>All persons are encouraged to review and implement this
295 specification and return comments to the (<a
297 public mailing list <a
300 Members can also send comments directly to the CSS Working
301 Group.
304 <p>This is still a draft document and may be updated, replaced, or
305 obsoleted by other documents at any time. It is inappropriate to
310 The English version of this specification is the only normative
311 version.
319 <ul>
323 </ul>
333 </ul>
335 <ul>
337 </ul>
340 <li class="tocline4"><a href="#attribute-representation">6.3.1. Representation of attributes and attributes values</a>
344 </ul>
354 <ul>
367 </ul>
369 </ul>
370 </li>
371 </ul>
373 <ul>
378 </ul>
385 <li class="tocline4"><a href="#adjacent-sibling-combinators">8.3.1. Adjacent sibling combinator</a>
386 <li class="tocline4"><a href="#general-sibling-combinators">8.3.2. General sibling combinator</a></li>
387 </ul>
388 </li>
389 </ul>
395 </ul>
402 </ul>
404 </div>
410 <p>Some features of this specification are specific to CSS, or have
411 particular limitations or rules specific to CSS. In this
412 specification, these have been described in terms of CSS2.1. <a
417 <p>All of the text of this specification is normative except
418 examples, notes, and sections explicitly marked as
419 non-normative.</p>
425 <p>The main differences between the selectors in CSS2 and those in
426 Selectors are:
428 <ul>
430 <li>the list of basic definitions (selector, group of selectors,
431 simple selector, etc.) has been changed; in particular, what was
432 referred to in CSS2 as a simple selector is now called a sequence
433 of simple selectors, and the term "simple selector" is now used for
434 the components of this sequence</li>
436 <li>an optional namespace component is now allowed in type element
437 selectors, the universal selector and attribute selectors</li>
441 <li>new simple selectors including substring matching attribute
442 selectors, and new pseudo-classes</li>
445 for pseudo-elements</li>
449 <li>profiles to be added to specifications integrating Selectors
450 and defining the set of selectors which is actually supported by
451 each specification</li>
453 <li>Selectors are now a CSS3 Module and an independent
454 specification; other specifications can now refer to this document
455 independently of CSS</li>
459 </ul>
463 <p><em>This section is non-normative, as it merely summarizes the
464 following sections.</em></p>
466 <p>A Selector represents a structure. This structure can be used as a
467 condition (e.g. in a CSS rule) that determines which elements a
468 selector matches in the document tree, or as a flat description of the
469 HTML or XML fragment corresponding to that structure.</p>
471 <p>Selectors may range from simple element names to rich contextual
472 representations.</p>
477 <thead>
478 <tr>
483 <tbody>
484 <tr>
489 selector</a></td>
491 <tr>
497 <tr>
502 selectors</a></td>
504 <tr>
510 selectors</a></td>
512 <tr>
518 selectors</a></td>
520 <tr>
526 selectors</a></td>
528 <tr>
534 selectors</a></td>
536 <tr>
542 selectors</a></td>
544 <tr>
550 selectors</a></td>
552 <tr>
557 pseudo-classes</a></td>
559 <tr>
564 pseudo-classes</a></td>
566 <tr>
569 from the last one</td>
572 pseudo-classes</a></td>
574 <tr>
579 pseudo-classes</a></td>
581 <tr>
584 from the last one</td>
587 pseudo-classes</a></td>
589 <tr>
594 pseudo-classes</a></td>
596 <tr>
601 pseudo-classes</a></td>
603 <tr>
608 pseudo-classes</a></td>
610 <tr>
615 pseudo-classes</a></td>
617 <tr>
622 pseudo-classes</a></td>
624 <tr>
629 pseudo-classes</a></td>
631 <tr>
634 nodes)</td>
637 pseudo-classes</a></td>
639 <tr>
642 which the target is not yet visited (:link) or already visited
643 (:visited)</td>
646 pseudo-classes</a></td>
648 <tr>
653 action pseudo-classes</a></td>
655 <tr>
660 pseudo-class</a></td>
662 <tr>
665 language specifies how language is determined)</td>
668 pseudo-class</a></td>
670 <tr>
673 disabled</td>
676 pseudo-classes</a></td>
678 <tr>
684 pseudo-classes</a></td>
686 <tr>
691 pseudo-element</a></td>
693 <tr>
698 pseudo-element</a></td>
700 <tr>
703 selected/highlighted by the user</td>
706 fragments pseudo-elements</a></td>
708 <tr>
713 pseudo-element</a></td>
715 <tr>
720 pseudo-element</a></td>
722 <tr>
728 selectors</a></td>
730 <tr>
735 selectors</a></td>
737 <tr>
742 pseudo-class</a></td>
744 <tr>
749 combinator</a></td>
751 <tr>
756 combinator</a></td>
758 <tr>
764 <tr>
771 <p>The meaning of each selector is derived from the table above by
773 column.</p>
777 <p>The case sensitivity of document language element names, attribute
778 names, and attribute values in selectors depends on the document
779 language. For example, in HTML, element names are case-insensitive,
780 but in XML, they are case-sensitive.</p>
793 selector or universal selector is allowed in the sequence.</p>
805 sequence of simple selectors.</p>
810 space may appear between a combinator and the simple selectors around
815 never part of white space.</p>
817 <p>The elements of a document tree that are represented by a selector
819 selector consisting of a single sequence of simple selectors
820 represents any element satisfying its requirements. Prepending another
821 sequence of simple selectors and a combinator to a sequence imposes
822 additional matching constraints, so the subjects of a selector are
823 always a subset of the elements represented by the last sequence of
824 simple selectors.</p>
826 <p>An empty selector, containing no sequence of simple selectors and
832 <p>When several selectors share the same declarations, they may be
837 <p>In this example, we condense three rules with identical
838 declarations into one. Thus,</p>
839 <pre>h1 { font-family: sans-serif }
840 h2 { font-family: sans-serif }
841 h3 { font-family: sans-serif }</pre>
844 </div>
847 because all the selectors are valid selectors. If just one of these
848 selectors were invalid, the entire group of selectors would be
849 invalid. This would invalidate the rule for all three heading
850 elements, whereas in the former case only one of the three individual
851 heading rules would be invalidated.</p>
859 element type. A type selector represents an instance of the element
860 type in the document tree.</p>
866 </div>
873 that has been previously declared may be prepended to the element name
877 <p>The namespace component may be left empty to indicate that the
878 selector is only to represent elements with no declared namespace.</p>
880 <p>An asterisk may be used for the namespace prefix, indicating that
881 the selector represents elements in any namespace (including elements
882 with no namespace).</p>
884 <p>Element type selectors that have no namespace component (no
885 namespace separator), represent elements without regard to the
886 element's namespace (equivalent to "<code>*|</code>") unless a default
887 namespace has been declared. If a default namespace has been declared,
888 the selector will represent only elements in the default
889 namespace.</p>
891 <p>A type selector containing a namespace prefix that has not been
893 The mechanism for declaring a namespace prefix is left up to the
894 language implementing Selectors. In CSS, such a mechanism is defined
895 in the General Syntax module.</p>
897 <p>In a namespace-aware client, element type selectors will only match
898 against the <a
900 of the element's <a
903 behaviors in down-level clients.</p>
907 <dl>
911 <dd>elements with name E in any namespace, including those without any
912 declared namespace</dd>
916 <dd>if no default namespace has been specified, this is equivalent to *|E.
917 Otherwise it is equivalent to ns|E where ns is the default namespace.</dd>
918 </dl>
923 <pre>@namespace foo url(http://www.example.com);
924 foo|h1 { color: blue }
925 foo|* { color: yellow }
926 |h1 { color: red }
927 *|h1 { color: green }
928 h1 { color: green }</pre>
933 <p>The second rule will match all elements in the
937 any declared namespace.</p>
940 namespace (including those without any declared namespace).</p>
942 <p>The last rule is equivalent to the fourth rule because no default
943 namespace has been defined.</p>
945 </div>
951 type. It represents any single element in the document tree in any
952 namespace (including those without any declared namespace) if no
953 default namespace has been specified. If a default namespace has been
957 <p>If the universal selector is not the only component of a sequence
962 <ul>
966 </ul>
967 </div>
971 omitted.</p>
975 <p>The universal selector allows an optional namespace component. It
976 is used as follows:</p>
978 <dl>
986 <dd>if no default namespace has been specified, this is equivalent to *|*.
987 Otherwise it is equivalent to ns|* where ns is the default namespace.</dd>
988 </dl>
990 <p>A universal selector containing a namespace prefix that has not
992 selector. The mechanism for declaring a namespace prefix is left up
993 to the language implementing Selectors. In CSS, such a mechanism is
994 defined in the General Syntax module.</p>
999 <p>Selectors allow the representation of an element's attributes. When
1000 a selector is used as an expression to match against an element,
1001 attribute selectors must be considered to match an element if that
1002 element has an attribute that matches the attribute represented by the
1003 attribute selector.</p>
1006 selectors</a></h4>
1010 <dl>
1013 the attribute.</dd>
1022 spaces).</dd>
1032 </dl>
1034 <p>Attribute values must be identifiers or strings. The
1035 case-sensitivity of attribute names and values in selectors depends on
1036 the document language.</p>
1044 value:</p>
1048 <p>In the following example, the selector represents a
1054 <p>Multiple attribute selectors can be used to represent several
1055 attributes of an element, or several conditions on the same
1064 and "~=". The first selector will represent, for example, the value
1084 <p>Similarly, the following selectors represents a
1088 <pre>DIALOGUE[character=romeo]
1089 DIALOGUE[character=juliet]</pre>
1091 </div>
1094 selectors</h4>
1096 <p>Three additional attribute selectors are provided for matching
1097 substrings in the value of an attribute:</p>
1099 <dl>
1109 </dl>
1111 <p>Attribute values must be identifiers or strings. The
1112 case-sensitivity of attribute names in selectors depends on the
1113 document language.</p>
1118 image:</p>
1126 </div>
1130 <p>Attribute selectors allow an optional namespace component to the
1131 attribute name. A namespace prefix that has been previously declared
1132 may be prepended to the attribute name separated by the namespace
1134 the Namespaces in the XML recommendation, default namespaces do not
1135 apply to attributes, therefore attribute selectors without a namespace
1136 component apply only to attributes that have no declared namespace
1137 (equivalent to "<code>|attr</code>"). An asterisk may be used for the
1138 namespace prefix indicating that the selector is to match all
1139 attribute names without regard to the attribute's namespace.
1141 <p>An attribute selector with an attribute name containing a namespace
1142 prefix that has not been previously declared is an <a
1144 a namespace prefix is left up to the language implementing Selectors.
1145 In CSS, such a mechanism is defined in the General Syntax module.
1150 [foo|att=val] { color: blue }
1151 [*|att] { color: yellow }
1152 [|att] { color: green }
1153 [att] { color: green }</pre>
1155 <p>The first rule will match only elements with the attribute
1159 <p>The second rule will match only elements with the attribute
1161 (including no declared namespace).</p>
1163 <p>The last two rules are equivalent and will match only elements
1165 declared to be in a namespace.</p>
1167 </div>
1171 <p>Attribute selectors represent explicitly set attribute values in
1172 the document tree. Default attribute values may be defined in a DTD or
1173 elsewhere, but cannot always be selected by attribute
1174 selectors. Selectors should be designed so that they work even if the
1175 default values are not included in the document tree.</p>
1184 knowledge of that namespace to treat default attribute values as if
1185 they were present in the document. (For example, an XHTML UA is not
1186 required to use its built-in knowledge of the XHTML DTD.)</p>
1189 choose to ignore external subsets.</p>
1201 <pre>EXAMPLE[notation=decimal] { /*... default property settings ...*/ }
1202 EXAMPLE[notation=octal] { /*... other settings...*/ }</pre>
1205 is set by default, i.e. not set explicitly. To catch all cases, the
1206 attribute selector for the default value must be dropped:</p>
1208 <pre>EXAMPLE { /*... default property settings ...*/ }
1209 EXAMPLE[notation=octal] { /*... other settings...*/ }</pre>
1212 more specific than the tag
1213 selector alone, the style declarations in the second rule will override
1214 those in the first for elements that have a "notation" attribute value
1215 of "octal". Care has to be taken that all property declarations that
1216 are to apply only to the default case are overridden in the non-default
1217 cases' style rules.</p>
1219 </div>
1227 the same meaning. The attribute value must immediately follow the
1230 <p>UAs may apply selectors using the period (.) notation in XML
1231 documents if the UA has namespace-specific knowledge that allows it to
1233 respective namespace. One such example of namespace-specific knowledge
1234 is the prose in the specification for a particular namespace (e.g. SVG
1245 <p>We can assign style information to all elements with
1254 <p>The following assigns style only to H1 elements with
1259 <p>Given these rules, the first H1 instance below would not have
1260 green text, while the second would:</p>
1265 </div>
1275 has been assigned a list of <a
1285 </div>
1288 power to the "class" attribute, authors could conceivably design their
1289 own "document language" based on elements with almost no associated
1290 presentation (such as DIV and SPAN in HTML) and assigning style
1291 information through the "class" attribute. Authors should avoid this
1292 practice since the structural elements of a document language often
1293 have recognized and accepted meanings and author-defined classes may
1294 not.</p>
1297 class attributes, their values must be concatenated with spaces
1298 between the values before searching for the class. As of this time the
1299 working group is not aware of any manner in which this situation can
1300 be reached, however, so this behavior is explicitly non-normative in
1301 this specification.</p>
1305 <p>Document languages may contain attributes that are declared to be
1306 of type ID. What makes attributes of type ID special is that no two
1307 such attributes can have the same value in a document, regardless of
1308 the type of the elements that carry them; whatever the document
1309 language, an ID typed attribute can be used to uniquely identify its
1310 element. In HTML all ID attributes are named "id"; XML applications
1311 may name ID attributes differently, but the same restriction
1312 applies.</p>
1314 <p>An ID-typed attribute of a document language allows authors to
1315 assign an identifier to one element instance in the document tree. W3C
1316 ID selectors represent an element instance based on its identifier. An
1319 identifier.</p>
1321 <p>Selectors does not specify how a UA knows the ID-typed attribute of
1322 an element. The UA may, e.g., read a document's DTD, have the
1323 information hard-coded or ask the user.
1330 <p>The following ID selector represents any element whose ID-typed
1333 <p>The following selector represents any element whose ID-typed
1336 </div>
1340 contains an element's IDs is contained in a DTD or a schema. When
1341 parsing XML, UAs do not always read the DTD, and thus may not know
1342 what the ID of an element is (though a UA may have namespace-specific
1343 knowledge that allows it to determine which attribute is the ID
1344 attribute for that namespace). If a style sheet designer knows or
1345 suspects that a UA may not know what the ID of an element is, he
1346 should use normal attribute selectors instead:
1350 <p>If an element has multiple ID attributes, all of them must be
1351 treated as IDs for that element for the purposes of the ID
1352 selector. Such a situation could be reached using mixtures of xml:id,
1353 DOM3 Core, XML DTDs, and namespace-specific knowledge.</p>
1357 <p>The pseudo-class concept is introduced to permit selection based on
1358 information that lies outside of the document tree or that cannot be
1359 expressed using the other simple selectors.</p>
1363 optionally by a value between parentheses.</p>
1365 <p>Pseudo-classes are allowed in all sequences of simple selectors
1366 contained in a selector. Pseudo-classes are allowed anywhere in
1367 sequences of simple selectors, after the leading type selector or
1368 universal selector (possibly omitted). Pseudo-class names are
1369 case-insensitive. Some pseudo-classes are mutually exclusive, while
1370 others can be applied simultaneously to the same
1371 element. Pseudo-classes may be dynamic, in the sense that an element
1372 may acquire or lose a pseudo-class while a user interacts with the
1373 document.</p>
1378 <p>Dynamic pseudo-classes classify elements on characteristics other
1379 than their name, attributes, or content, in principle characteristics
1380 that cannot be deduced from the document tree.</p>
1382 <p>Dynamic pseudo-classes do not appear in the document source or
1383 document tree.</p>
1388 <p>User agents commonly display unvisited links differently from
1389 previously visited ones. Selectors
1393 <ul>
1395 not yet been visited.</li>
1397 been visited by the user. </li>
1398 </ul>
1400 <p>After some amount of time, user agents may choose to return a
1401 visited link to the (unvisited) ':link' state.</p>
1409 <p>The following selector represents links carrying class
1414 </div>
1417 authors to abuse the :link and :visited pseudo-classes to determine
1418 which sites a user has visited without the user's consent.
1420 <p>UAs may therefore treat all links as unvisited links, or implement
1421 other measures to preserve the user's privacy while rendering visited
1422 and unvisited links differently.</p>
1425 :hover, :active, and :focus</a></h5>
1427 <p>Interactive user agents sometimes change the rendering in response
1428 to user actions. Selectors provides
1429 three pseudo-classes for the selection of an element the user is
1430 acting on.</p>
1432 <ul>
1435 designates an element with a pointing device, but does not activate
1436 it. For example, a visual user agent could apply this pseudo-class
1437 when the cursor (mouse pointer) hovers over a box generated by the
1438 element. User agents not that do not support <a
1440 media</a> do not have to support this pseudo-class. Some conforming
1441 user agents that support <a
1443 media</a> may not be able to support this pseudo-class (e.g., a pen
1444 device that does not detect hovering).</li>
1447 is being activated by the user. For example, between the times the
1448 user presses the mouse button and releases it.</li>
1451 has the focus (accepts keyboard or mouse events, or other forms of
1452 input). </li>
1454 </ul>
1456 <p>There may be document language or implementation specific limits on
1460 <p>These pseudo-classes are not mutually exclusive. An element may
1461 match several pseudo-classes at the same time.</p>
1463 <p>Selectors doesn't define if the parent of an element that is
1464 ':active' or ':hover' is also in that state.</p>
1468 <pre>a:link /* unvisited links */
1469 a:visited /* visited links */
1470 a:hover /* user hovers */
1471 a:active /* active links */</pre>
1473 <pre>a:focus
1474 a:focus:hover</pre>
1476 the pseudo-class :focus and in the pseudo-class :hover.</p>
1477 </div>
1480 and ':active' (or ':link' and ':active').</p>
1484 <p>Some URIs refer to a location within a resource. This kind of URI
1486 identifier (called the fragment identifier).</p>
1488 <p>URIs with fragment identifiers link to a certain element within the
1489 document, known as the target element. For instance, here is a URI
1491 document:</p>
1496 pseudo-class. If the document's URI has no fragment identifier, then
1497 the document has no target element.</p>
1504 URI.</p>
1505 </div>
1510 target element red and place an image before it, if there is one:</p>
1511 <pre>*:target { color : red }
1512 *:target::before { content : url(target.png) }</pre>
1513 </div>
1517 <p>If the document language specifies how the human language of an
1518 element is determined, it is possible to write selectors that
1519 represent an element based on its language. For example, in HTML <a
1522 element, and possibly by information from the protocol (such as HTTP
1524 there may be other document language-specific methods for determining
1525 the language.</p>
1528 is in language C. Whether an element is represented by a
1530 being either equal to, or a hyphen-separated substring of, the
1531 element's language value, in the same way as if performed by the <a
1533 selectors. The identifier C does not have to be a valid language
1534 name.</p>
1548 <p>The two following selectors represent an HTML document that is in
1549 Belgian, French, or German. The two next selectors represent
1551 or German.</p>
1552 <pre>html:lang(fr-be)
1553 html:lang(de)
1554 :lang(fr-be) > q
1556 </div>
1563 the look of user interface elements that are enabled — which the
1564 user can select or activate in some fashion (e.g. clicking on a button
1565 with a mouse). There is a need for such a pseudo-class because there
1566 is no way to programmatically specify the default appearance of say,
1568 would look like when it was disabled.</p>
1571 author to specify precisely how a disabled or inactive user interface
1572 element should look.</p>
1574 <p>Most elements will be neither enabled nor disabled. An element is
1575 enabled if the user can either activate it or transfer the focus to
1576 it. An element is disabled if it could be enabled, but the user cannot
1577 presently activate it or transfer focus to it.</p>
1582 <p>Radio and checkbox elements can be toggled by the user. Some menu
1583 items are "checked" when the user selects them. When such elements are
1587 attributes as described in <a
1592 in nature, and is altered by user action, since it can also be based
1601 <p>Radio and checkbox elements can be toggled by the user, but are
1602 sometimes in an indeterminate state, neither checked nor unchecked.
1603 This can be due to an element attribute, or DOM manipulation.</p>
1605 <p>A future version of this specification may introduce an
1607 <!--While the <code>:indeterminate</code> pseudo-class is dynamic in
1608 nature, and is altered by user action, since it can also be based on
1609 the presence of an element attribute, it applies to all media.</p>
1611 <p>Components of a radio-group initialized with no pre-selected choice
1614 </div>
1620 pseudo-classes</dfn> to permit selection based on extra information that lies in
1621 the document tree but cannot be represented by other simple selectors or
1622 combinators.
1624 <p>Note that standalone pieces of PCDATA (text nodes in the DOM) are
1625 not counted when calculating the position of an element in the list of
1626 children of its parent. When calculating the position of an element in
1627 the list of children of its parent, the index numbering starts at 1.
1633 the root of the document. In HTML 4, this is always the
1639 <p>The
1641 pseudo-class notation represents an element that has
1647 each. For example, this allows the selectors to address every other
1648 row in a table, and could be used to alternate the color
1651 integers. The index of the first child of an element is 1.
1662 tr:nth-child(odd) /* same */
1663 tr:nth-child(2n) /* represents every even row of an HTML table */
1664 tr:nth-child(even) /* same */
1666 /* Alternate paragraph colours in CSS */
1671 </div>
1676 included, so the syntax simplifies to
1684 </div>
1692 bar:nth-child(n+0) /* same */
1693 bar:nth-child(n) /* same */
1695 </div>
1704 </div>
1707 pseudo-class represents no element in the document tree.</p>
1712 tree.</p>
1717 </div>
1720 expression must be removed (it is effectively replaced by the "-"
1728 </div>
1734 pseudo-class notation represents an element that has
1740 as arguments.
1747 foo:nth-last-child(odd) /* represents all odd foo elements in their parent element,
1748 counting from the last one */</pre>
1749 </div>
1755 pseudo-class notation represents an element that has
1760 of that type after all the children of that type have been split into
1762 for the syntax of its argument. It also accepts the
1771 </div>
1777 pseudo-class notation represents an element that has
1789 following selector:</p>
1792 selector ends up being just as long:</p>
1794 </div>
1800 represents an element that is the first child of some other element.
1814 fragment:
1822 a:first-child /* Same (assuming a is not the root element) */</pre>
1823 </div>
1828 represents an element that is the last child of some other element.
1835 </div>
1840 represents an element that is the first sibling of its type in the list of
1841 children of its parent element.
1845 <p>The following selector represents a definition title
1848 its parent element.</p>
1851 elements in the following example but not for the third one:</p>
1863 </div>
1869 the last sibling of its type in the list of children of its parent
1870 element.</p>
1874 <p>The following selector represents the last data cell
1877 </div>
1881 <p>Represents an element that has a parent element and whose parent
1882 element has no other element children. Same as
1885 specificity.</p>
1889 <p>Represents an element that has a parent element and whose parent
1890 element has no other element children with the same element name. Same
1893 specificity.</p>
1899 no children at all. In terms of the DOM, only element nodes and text
1900 nodes (including CDATA nodes and entity references) whose data has a
1901 non-zero length must be considered as affecting emptiness; comments,
1902 PIs, and other nodes must not affect whether an element is considered
1903 empty or not.</p>
1910 following fragments:</p>
1914 </div>
1916 <h4><a name=content-selectors>6.6.6. Blank</a></h4> <!-- It's the Return of Appendix H!!! Run away! -->
1919 <!-- (used to be :contains()) -->
1925 selector</a> (excluding the negation pseudo-class itself and
1926 pseudo-elements) as an argument. It represents an element that is not
1927 represented by the argument.
1929 <!-- pseudo-elements are not simple selectors, so the above paragraph
1930 may be a bit confusing -->
1935 elements in an HTML document that are not disabled.</p>
1938 elements.</p>
1940 <p>The following group of selectors represents all HTML elements
1941 except links.</p>
1943 </div>
1945 <p>Default namespace declarations do not affect the argument of the
1946 negation pseudo-class unless the argument is a universal selector or a
1947 type selector.</p>
1951 <p>Assuming that the default namespace is bound to
1952 "http://example.com/", the following selector represents all
1953 elements that are not in that namespace:</p>
1955 <p>The following CSS selector matches any element being hovered,
1956 regardless of its namespace. In particular, it is not limited to
1957 only matching elements in the default namespace that are not being
1958 hovered, and elements not in the default namespace don't match the
1961 </div>
1967 specificity.</p>
1971 <p>Pseudo-elements create abstractions about the document tree beyond
1972 those specified by the document language. For instance, document
1973 languages do not offer mechanisms to access the first letter or first
1974 line of an element's content. Pseudo-elements allow designers to refer
1975 to this otherwise inaccessible information. Pseudo-elements may also
1976 provide designers a way to refer to content that does not exist in the
1979 content).</p>
1982 by the name of the pseudo-element.</p>
1985 in order to establish a discrimination between pseudo-classes and
1986 pseudo-elements. For compatibility with existing style sheets, user
1987 agents must also accept the previous one-colon notation for
1993 <p>Only one pseudo-element may appear per selector, and if present it
1994 must appear after the sequence of simple selectors that represents the
1996 future version of this specification may allow multiple
1997 pesudo-elements per selector.</span></p>
2002 of the first formatted line of an element.
2009 </div>
2012 HTML element. It does match a pseudo-element that conforming user
2013 agents will insert at the beginning of every paragraph.</p>
2015 <p>Note that the length of the first line depends on a number of
2016 factors, including the width of the page, the font size, etc. Thus,
2017 an ordinary HTML paragraph such as:</p>
2019 <pre>
2021 paragraph that will be broken into several
2022 lines. The first line will be identified
2023 by a fictional tag sequence. The other lines
2024 will be treated as ordinary lines in the
2026 </pre>
2028 <p>the lines of which happen to be broken as follows:
2030 <pre>
2031 THIS IS A SOMEWHAT LONG HTML PARAGRAPH THAT
2032 will be broken into several lines. The first
2033 line will be identified by a fictional tag
2034 sequence. The other lines will be treated as
2035 ordinary lines in the paragraph.
2036 </pre>
2040 fictional tag sequence helps to show how properties are inherited.</p>
2042 <pre>
2045 lines. The first line will be identified
2046 by a fictional tag sequence. The other lines
2047 will be treated as ordinary lines in the
2049 </pre>
2051 <p>If a pseudo-element breaks up a real element, the desired effect
2052 can often be described by a fictional tag sequence that closes and
2053 then re-opens the element. Thus, if we mark up the previous paragraph
2056 <pre>
2058 paragraph that will be broken into several
2060 by a fictional tag sequence. The other lines
2061 will be treated as ordinary lines in the
2063 </pre>
2065 <p>the user agent could simulate start and end tags for
2069 <pre>
2071 somewhat long HTML
2072 paragraph that will <b></SPAN></b></P::first-line><b><SPAN class="test"></b> be
2073 broken into several
2075 by a fictional tag sequence. The other lines
2076 will be treated as ordinary lines in the
2078 </pre>
2081 attached to a block-level element, an inline-block, a table-caption,
2082 or a table-cell.</p>
2085 element may occur inside a
2086 block-level descendant in the same flow (i.e., a block-level
2087 descendant that is not positioned and not a float). E.g., the first
2092 <p>The first line of a table-cell or inline-block cannot be the first
2103 <p>A UA should act as if the fictional start tags of the
2105 innermost enclosing block-level element. (Since CSS1 and CSS2 were
2106 silent on this case, authors should not rely on this behavior.) Here
2107 is an example. The fictional tag sequence for</p>
2109 <pre>
2114 </pre>
2118 <pre>
2120 <P><DIV::first-line><P::first-line>First paragraph</P::first-line></DIV::first-line></P>
2123 </pre>
2126 inline-level element, but with certain restrictions. In CSS, the
2128 pseudo-element: font properties, color property, background
2129 properties, 'word-spacing', 'letter-spacing', 'text-decoration',
2130 'vertical-align', 'text-transform', 'line-height'. UAs may apply other
2131 properties as well.</p>
2137 letter of the first line of a block, if it is not preceded by any
2138 other content (such as images or inline tables) on its line. The
2140 caps", which are common typographical effects. This type of initial
2141 letter is similar to an inline-level element if its 'float' property
2142 is 'none'; otherwise, it is similar to a floated element.</p>
2145 pseudo-elements: font properties, 'text-decoration', 'text-transform',
2146 'letter-spacing', 'word-spacing' (when appropriate), 'line-height',
2147 'float', 'vertical-align' (only if 'float' is 'none'), margin
2148 properties, padding properties, border properties, color property,
2149 background properties. UAs may apply other properties as well. To
2150 allow UAs to render a typographically correct drop cap or initial cap,
2151 the UA may choose a line-height, width and height based on the shape
2152 of the letter, unlike for normal elements.</p>
2156 <p>This example shows a possible rendering of an initial cap. Note
2158 pseudo-element is 1.1, but the UA in this example has computed the
2159 height of the first letter differently, so that it doesn't cause any
2160 unnecessary space between the first two lines. Also note that the
2163 <pre>
2164 p { line-height: 1.1 }
2165 p::first-letter { font-size: 3em; font-weight: normal }
2166 span { font-weight: bold }
2167 ...
2171 En dagelix geschrey de bange stad ontzet.
2172 </pre>
2175 </div>
2176 </div>
2181 <pre>
2188 P::first-letter { font-size: 200%; font-weight: bold; float: left }
2189 SPAN { text-transform: uppercase }
2197 </pre>
2202 <P><img src="first-letter.gif" alt="Image illustrating the combined effect of the ::first-letter and ::first-line pseudo-elements"></p>
2203 </div>
2208 <pre>
2212 T
2215 few words of an article in the Economist.
2217 </pre>
2220 the content (i.e., the initial character), while the ::first-line
2221 pseudo-element start tag is inserted right after the start tag of the
2222 block element.</p> </div>
2224 <p>In order to achieve traditional drop caps formatting, user agents
2225 may approximate font sizes, for example to align baselines. Also, the
2226 glyph outline may be taken into account when formatting.</p>
2230 punctuation classes), that precedes or follows the first letter should
2236 </div>
2243 block, list-item, table-cell, table-caption, and inline-block
2245 may allow this pesudo-element to apply to more element
2246 types.</span></p>
2249 such elements that contain text, or that have a descendant in the same
2250 flow that contains text. A UA should act as if the fictional start tag
2251 of the ::first-letter pseudo-element is just before the first text of
2252 the element, even if that first text is in a descendant.</p>
2256 <p>The fictional tag sequence for this HTMLfragment:
2259 <p>is:
2262 </div>
2264 <p>The first letter of a table-cell or inline-block cannot be the
2277 <p>In CSS, if an element is a list item ('display: list-item'), the
2279 principal box after the marker. UAs may ignore
2289 </div>
2291 <p>Some languages may have specific rules about how to treat certain
2292 letter combinations. In Dutch, for example, if the letter combination
2293 "ij" appears at the beginning of a word, both letters should be
2296 <p>If the letters that would form the ::first-letter are not in the
2298 may create a ::first-letter pseudo-element from one of the elements,
2299 both elements, or simply not create a pseudo-element.</p>
2301 <p>Similarly, if the first letter(s) of the block are not at the start
2302 of the line (for example due to bidirectional reordering), then the UA
2303 need not create the pseudo-element(s).
2308 how overlapping pseudo-elements may interact. The first letter of
2309 each P element will be green with a font size of '24pt'. The rest of
2310 the first formatted line will be 'blue' while the rest of the
2311 paragraph will be 'red'.</p>
2314 p::first-letter { color: green; font-size: 200% }
2315 p::first-line { color: blue }
2326 S
2329 ends up on two lines
2336 </div>
2342 of a document that has been highlighted by the user. This also
2343 applies, for example, to selected text within an editable text
2344 field. This pseudo-element should not be confused with the <code><a
2349 nature, and is altered by user action, it is reasonable to expect that
2350 when a UA re-renders to a static medium (such as a printed page, see
2352 dynamic medium (like screen), the UA may wish to transfer the current
2354 appropriate formatting and rendering take effect as well. This is not
2356 pseudo-element for static media.
2359 pseudo-elements: color, background, cursor (optional), outline
2360 (optional). The computed value of the 'background-image' property on
2367 can be used to describe generated content before or after an element's
2374 element including the inserted text.</p>
2380 <p>At times, authors may want selectors to describe an element that is
2381 the descendant of another element in the document tree (e.g., "an
2382 <code>EM</code> element that is contained within an <code>H1</code>
2383 element"). Descendant combinators express such a relationship. A
2385 separates two sequences of simple selectors. A selector of the form
2395 description of the following fragment:</p>
2402 either side of the "*" is not part of the universal selector; the
2403 whitespace is a combinator indicating that the DIV must be the
2404 ancestor of some element, and that that element must be an ancestor
2405 of the P.</p>
2406 <p>The following selector, which combines descendant combinators and
2411 </div>
2416 between two elements. A child combinator is made of the
2418 separates two sequences of simple selectors.
2426 <p>The following example combines descendant combinators and child
2427 combinators.</p>
2434 </div>
2436 <p>For information on selecting the first child of an element, please
2437 see the section on the <code><a
2439 above.</p>
2443 <p>There are two different sibling combinators: the adjacent sibling
2444 combinator and the general sibling combinator. In both cases,
2445 non-element nodes (e.g. text between elements) are ignored when
2446 considering adjacency of elements.</p>
2452 sequences of simple selectors. The elements represented by the two
2453 sequences share the same parent in the document tree and the element
2454 represented by the first sequence immediately precedes the element
2455 represented by the second one.</p>
2462 <p>The following selector is conceptually similar to the one in the
2463 previous example, except that it adds an attribute selector — it
2467 </div>
2474 simple selectors. The elements represented by the two sequences share
2475 the same parent in the document tree and the element represented by
2476 the first sequence precedes (not necessarily immediately) the element
2477 represented by the second one.</p>
2483 is a correct and valid, but partial, description of:</p>
2487 </div>
2493 <ul>
2495 <li>count the number of class selectors, attributes selectors, and pseudo-classes in the selector (= b)</li>
2498 </ul>
2501 are counted like any other, but the negation itself does not count as
2502 a pseudo-class.</p>
2504 <p>Concatenating the three numbers a-b-c (in a number system with a
2505 large base) gives the specificity.</p>
2518 </pre>
2519 </div>
2529 <p>The grammar below defines the syntax of Selectors. It is globally
2531 it directly, since it doesn't express the parsing conventions). The
2532 format of the productions is optimized for human consumption and some
2534 are used:</p>
2536 <ul>
2542 </ul>
2546 <pre>selectors_group
2547 : selector [ COMMA S* selector ]*
2548 ;
2550 selector
2551 : simple_selector_sequence [ combinator simple_selector_sequence ]*
2552 ;
2554 combinator
2555 /* combinators can be surrounded by white space */
2556 : PLUS S* | GREATER S* | TILDE S* | S+
2557 ;
2559 simple_selector_sequence
2560 : [ type_selector | universal ]
2561 [ HASH | class | attrib | pseudo | negation ]*
2562 | [ HASH | class | attrib | pseudo | negation ]+
2563 ;
2565 type_selector
2566 : [ namespace_prefix ]? element_name
2567 ;
2569 namespace_prefix
2570 : [ IDENT | '*' ]? '|'
2571 ;
2573 element_name
2574 : IDENT
2575 ;
2577 universal
2578 : [ namespace_prefix ]? '*'
2579 ;
2581 class
2582 : '.' IDENT
2583 ;
2585 attrib
2586 : '[' S* [ namespace_prefix ]? IDENT S*
2587 [ [ PREFIXMATCH |
2588 SUFFIXMATCH |
2589 SUBSTRINGMATCH |
2590 '=' |
2591 INCLUDES |
2592 DASHMATCH ] S* [ IDENT | STRING ] S*
2593 ]? ']'
2594 ;
2596 pseudo
2597 /* '::' starts a pseudo-element, ':' a pseudo-class */
2598 /* Exceptions: :first-line, :first-letter, :before and :after. */
2599 /* Note that pseudo-elements are restricted to one per selector and */
2600 /* occur only in the last simple_selector_sequence. */
2601 : ':' ':'? [ IDENT | functional_pseudo ]
2602 ;
2604 functional_pseudo
2605 : FUNCTION S* expression ')'
2606 ;
2608 expression
2609 /* In CSS3, the expressions are identifiers, strings, */
2610 /* or of the form "an+b" */
2611 : [ [ PLUS | '-' | DIMENSION | NUMBER | STRING | IDENT ] S* ]+
2612 ;
2614 negation
2615 : NOT S* negation_arg S* ')'
2616 ;
2618 negation_arg
2619 : type_selector | universal | HASH | class | attrib | pseudo
2620 ;</pre>
2627 case-insensitive.</p>
2630 number that current versions of Flex can deal with (decimal 255). They
2635 <pre>%option case-insensitive
2637 ident [-]?{nmstart}{nmchar}*
2638 name {nmchar}+
2639 nmstart [_a-z]|{nonascii}|{escape}
2642 escape {unicode}|\\[^\n\r\f0-9a-f]
2643 nmchar [_a-z0-9-]|{nonascii}|{escape}
2645 string {string1}|{string2}
2647 string2 \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*\'
2648 invalid {invalid1}|{invalid2}
2650 invalid2 \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*
2651 nl \n|\r\n|\r|\f
2652 w [ \t\r\n\f]*
2654 %%
2656 [ \t\r\n\f]+ return S;
2663 {ident} return IDENT;
2664 {string} return STRING;
2666 {num} return NUMBER;
2673 @{ident} return ATKEYWORD;
2674 {invalid} return INVALID;
2675 {num}% return PERCENTAGE;
2676 {num}{ident} return DIMENSION;
2682 U\+[0-9a-f?]{1,6}(-[0-9a-f]{1,6})? return UNICODE_RANGE;
2684 \/\*[^*]*\*+([^/*][^*]*\*+)*\/ /* ignore comments */
2686 . return *yytext;</pre>
2690 <h2><a name=downlevel>11. Namespaces and down-level clients</a></h2>
2692 <p>An important issue is the interaction of CSS selectors with XML
2693 documents in web clients that were produced prior to this
2694 document. Unfortunately, due to the fact that namespaces must be
2695 matched based on the URI which identifies the namespace, not the
2696 namespace prefix, some mechanism is required to identify namespaces in
2697 CSS by their URI as well. Without such a mechanism, it is impossible
2698 to construct a CSS style sheet which will properly match selectors in
2699 all cases against a random set of XML documents. However, given
2700 complete knowledge of the XML document to which a style sheet is to be
2701 applied, and a limited use of namespaces within the XML document, it
2702 is possible to construct a style sheet in which selectors would match
2703 elements and attributes correctly.</p>
2705 <p>It should be noted that a down-level CSS client will (if it
2706 properly conforms to CSS forward compatible parsing rules) ignore all
2707 <code>@namespace</code> at-rules, as well as all style rules that make
2708 use of namespace qualified element type or attribute selectors. The
2709 syntax of delimiting namespace prefixes in CSS was deliberately chosen
2710 so that down-level CSS clients would ignore the style rules rather
2711 than possibly match them incorrectly.</p>
2713 <p>The use of default namespaces in CSS makes it possible to write
2714 element type selectors that will function in both namespace aware CSS
2715 clients as well as down-level clients. It should be noted that
2716 down-level clients may incorrectly match selectors against XML
2717 elements in other namespaces.</p>
2719 <p>The following are scenarios and examples in which it is possible to
2720 construct style sheets which would function properly in web clients
2721 that do not implement this proposal.</p>
2723 <ol>
2724 <li>
2726 <p>The XML document does not use namespaces.</p>
2728 <ul>
2730 <li>In this case, it is obviously not necessary to declare or use
2731 namespaces in the style sheet. Standard CSS element type and
2732 attribute selectors will function adequately in a down-level
2733 client.</li>
2735 <li>In a CSS namespace aware client, the default behavior of
2736 element selectors matching without regard to namespace will
2737 function properly against all elements, since no namespaces are
2738 present. However, the use of specific element type selectors that
2740 will guarantee that selectors will match only XML elements that do
2741 not have a declared namespace. </li>
2743 </ul>
2745 </li>
2747 <li>
2749 <p>The XML document defines a single, default namespace used
2750 throughout the document. No namespace prefixes are used in element
2751 names.</p>
2753 <ul>
2755 <li>In this case, a down-level client will function as if
2756 namespaces were not used in the XML document at all. Standard CSS
2757 element type and attribute selectors will match against all
2758 elements. </li>
2760 </ul>
2762 </li>
2764 <li>
2766 <p>The XML document does <b>not</b> use a default namespace, all
2767 namespace prefixes used are known to the style sheet author, and
2768 there is a direct mapping between namespace prefixes and namespace
2769 URIs. (A given prefix may only be mapped to one namespace URI
2770 throughout the XML document; there may be multiple prefixes mapped
2771 to the same URI).</p>
2773 <ul>
2775 <li>In this case, the down-level client will view and match
2776 element type and attribute selectors based on their fully
2777 qualified name, not the local part as outlined in the <a
2780 to describe the fully qualified names, e.g.
2782 <code><html:h1></code>. Selectors using the qualified name
2783 will only match XML elements that use the same prefix. Other
2784 namespace prefixes used in the XML that are mapped to the same URI
2785 will not match as expected unless additional CSS style rules are
2786 declared for them.</li>
2788 <li>Note that selectors declared in this fashion will
2789 <em>only</em> match in down-level clients. A CSS namespace aware
2790 client will match element type and attribute selectors based on
2791 the name's local part. Selectors declared with the fully
2792 qualified name will not match (unless there is no namespace prefix
2793 in the fully qualified name).</li>
2795 </ul>
2797 </li>
2799 </ol>
2801 <p>In other scenarios: when the namespace prefixes used in the XML are
2802 not known in advance by the style sheet author; or a combination of
2803 elements with no namespace are used in conjunction with elements using
2804 a default namespace; or the same namespace prefix is mapped to
2805 <em>different</em> namespace URIs within the same document, or in
2806 different documents; it is impossible to construct a CSS style sheet
2807 that will function properly against all elements in those documents,
2808 unless, the style sheet is written using a namespace URI syntax (as
2809 outlined in this document or similar) and the document is processed by
2810 a CSS and XML namespace aware client.</p>
2812 <h2><a name=profiling>12. Profiles</a></h2>
2814 <p>Each specification using Selectors must define the subset of W3C
2815 Selectors it allows and excludes, and describe the local meaning of
2816 all the components of that subset.</p>
2818 <p>Non normative examples:
2822 <tbody>
2823 <tr>
2825 <tr>
2826 <th>Specification</th>
2827 <td>CSS level 1</td></tr>
2828 <tr>
2829 <th>Accepts</th>
2830 <td>type selectors<br>class selectors<br>ID selectors<br>:link,
2831 :visited and :active pseudo-classes<br>descendant combinator
2832 <br>::first-line and ::first-letter pseudo-elements</td></tr>
2833 <tr>
2834 <th>Excludes</th>
2835 <td>
2837 <p>universal selector<br>attribute selectors<br>:hover and :focus
2838 pseudo-classes<br>:target pseudo-class<br>:lang() pseudo-class<br>all UI
2839 element states pseudo-classes<br>all structural
2840 pseudo-classes<br>negation pseudo-class<br>all
2841 UI element fragments pseudo-elements<br>::before and ::after
2842 pseudo-elements<br>child combinators<br>sibling combinators
2844 <p>namespaces</td></tr>
2845 <tr>
2846 <th>Extra constraints</th>
2847 <td>only one class selector allowed per sequence of simple
2848 selectors</td></tr></tbody></table><br><br>
2850 <tbody>
2851 <tr>
2853 <tr>
2854 <th>Specification</th>
2855 <td>CSS level 2</td></tr>
2856 <tr>
2857 <th>Accepts</th>
2858 <td>type selectors<br>universal selector<br>attribute presence and
2859 values selectors<br>class selectors<br>ID selectors<br>:link, :visited,
2860 :active, :hover, :focus, :lang() and :first-child pseudo-classes
2861 <br>descendant combinator<br>child combinator<br>adjacent sibling
2862 combinator<br>::first-line and ::first-letter pseudo-elements<br>::before
2863 and ::after pseudo-elements</td></tr>
2864 <tr>
2865 <th>Excludes</th>
2866 <td>
2868 <p>content selectors<br>substring matching attribute
2869 selectors<br>:target pseudo-classes<br>all UI element
2870 states pseudo-classes<br>all structural pseudo-classes other
2871 than :first-child<br>negation pseudo-class<br>all UI element
2872 fragments pseudo-elements<br>general sibling combinators
2874 <p>namespaces</td></tr>
2875 <tr>
2876 <th>Extra constraints</th>
2877 <td>more than one class selector per sequence of simple selectors (CSS1
2878 constraint) allowed</td></tr></tbody></table>
2880 <p>In CSS, selectors express pattern matching rules that determine which style
2881 rules apply to elements in the document tree.
2883 <p>The following selector (CSS level 2) will <b>match</b> all anchors <code>a</code>
2884 with attribute <code>name</code> set inside a section 1 header <code>h1</code>:
2885 <pre>h1 a[name]</pre>
2887 <p>All CSS declarations attached to such a selector are applied to elements
2888 matching it. </div>
2892 <tbody>
2893 <tr>
2895 <tr>
2896 <th>Specification</th>
2897 <td>STTS 3</td>
2898 </tr>
2899 <tr>
2900 <th>Accepts</th>
2901 <td>
2903 <p>type selectors<br>universal selectors<br>attribute selectors<br>class
2904 selectors<br>ID selectors<br>all structural pseudo-classes<br>
2905 all combinators
2907 <p>namespaces</td></tr>
2908 <tr>
2909 <th>Excludes</th>
2910 <td>non-accepted pseudo-classes<br>pseudo-elements<br></td></tr>
2911 <tr>
2912 <th>Extra constraints</th>
2913 <td>some selectors and combinators are not allowed in fragment
2914 descriptions on the right side of STTS declarations.</td></tr></tbody></table>
2915 <form>
2941 </form>
2943 <p>Selectors can be used in STTS 3 in two different
2944 manners:
2945 <ol>
2946 <li>a selection mechanism equivalent to CSS selection mechanism: declarations
2947 attached to a given selector are applied to elements matching that selector,
2948 <li>fragment descriptions that appear on the right side of declarations.
2949 </li></ol></div>
2951 <h2><a name=Conformance></a>13. Conformance and requirements</h2>
2953 <p>This section defines conformance with the present specification only.
2955 <p>The inability of a user agent to implement part of this specification due to
2956 the limitations of a particular device (e.g., non interactive user agents will
2957 probably not implement dynamic pseudo-classes because they make no sense without
2958 interactivity) does not imply non-conformance.
2960 <p>All specifications reusing Selectors must contain a <a
2962 subset of Selectors it accepts or excludes, and describing the constraints
2963 it adds to the current specification.
2965 <p>Invalidity is caused by a parsing error, e.g. an unrecognized token or a token
2966 which is not allowed at the current parsing point.
2968 <p>User agents must observe the rules for handling parsing errors:
2969 <ul>
2970 <li>a simple selector containing an undeclared namespace prefix is invalid</li>
2971 <li>a selector containing an invalid simple selector, an invalid combinator
2972 or an invalid token is invalid. </li>
2973 <li>a group of selectors containing an invalid selector is invalid.</li>
2974 </ul>
2977 errors. (In the case of CSS, the entire rule in which the selector is
2978 used is dropped.)</p>
2980 <!-- Apparently all these references are out of date:
2981 <p>Implementations of this specification must behave as
2983 when parsing selectors and attempting matches. (In particular,
2984 implementations must assume the data is normalized and must not
2985 normalize it.) Normative rules for matching strings are defined in
2988 specification.</p>-->
2990 <h2><a name=Tests></a>14. Tests</h2>
2992 <p>This specification has <a
2994 suite</a> allowing user agents to verify their basic conformance to
2995 the specification. This test suite does not pretend to be exhaustive
2996 and does not cover all possible combined cases of Selectors.</p>
2998 <h2><a name=ACKS></a>15. Acknowledgements</h2>
3000 <p>The CSS working group would like to thank everyone who has sent
3001 comments on this specification over the years.</p>
3003 <p>The working group would like to extend special thanks to Donna
3004 McManus, Justin Baker, Joel Sklar, and Molly Ives Brower who perfermed
3005 the final editorial review.</p>
3007 <h2><a name=references>16. References</a></h2>
3011 <dt>[CSS1]
3012 <dd><a name=refsCSS1></a> Bert Bos, Håkon Wium Lie; "<cite>Cascading Style Sheets, level 1</cite>", W3C Recommendation, 17 Dec 1996, revised 11 Jan 1999
3015 <dt>[CSS21]
3016 <dd><a name=refsCSS21></a> Bert Bos, Tantek Çelik, Ian Hickson, Håkon Wium Lie, editors; "<cite>Cascading Style Sheets, level 2 revision 1</cite>", W3C Working Draft, 13 June 2005
3019 <dt>[CWWW]
3020 <dd><a name=refsCWWW></a> Martin J. Dürst, François Yergeau, Misha Wolf, Asmus Freytag, Tex Texin, editors; "<cite>Character Model for the World Wide Web</cite>", W3C Recommendation, 15 February 2005
3023 <dt>[FLEX]
3024 <dd><a name="refsFLEX"></a> "<cite>Flex: The Lexical Scanner Generator</cite>", Version 2.3.7, ISBN 1882114213
3026 <dt>[HTML4]
3027 <dd><a name="refsHTML4"></a> Dave Ragget, Arnaud Le Hors, Ian Jacobs, editors; "<cite>HTML 4.01 Specification</cite>", W3C Recommendation, 24 December 1999
3030 <dt>[MATH]
3031 <dd><a name="refsMATH"></a> Patrick Ion, Robert Miner, editors; "<cite>Mathematical Markup Language (MathML) 1.01</cite>", W3C Recommendation, revision of 7 July 1999
3032 <dd>(<code><a href="http://www.w3.org/TR/REC-MathML/">http://www.w3.org/TR/REC-MathML/</a></code>)
3034 <dt>[RFC3066]
3035 <dd><a name="refsRFC3066"></a> H. Alvestrand; "<cite>Tags for the Identification of Languages</cite>", Request for Comments 3066, January 2001
3036 <dd>(<a href="http://www.ietf.org/rfc/rfc3066.txt"><code>http://www.ietf.org/rfc/rfc3066.txt</code></a>)
3038 <dt>[STTS]
3039 <dd><a name=refsSTTS></a> Daniel Glazman; "<cite>Simple Tree Transformation Sheets 3</cite>", Electricité de France, submission to the W3C, 11 November 1998
3040 <dd>(<code><a href="http://www.w3.org/TR/NOTE-STTS3">http://www.w3.org/TR/NOTE-STTS3</a></code>)
3042 <dt>[SVG]
3043 <dd><a name="refsSVG"></a> Jon Ferraiolo, 藤沢 淳, Dean Jackson, editors; "<cite>Scalable Vector Graphics (SVG) 1.1 Specification</cite>", W3C Recommendation, 14 January 2003
3046 <dt>[UNICODE]</dt>
3048 href="http://www.unicode.org/versions/Unicode4.1.0/">The Unicode Standard, Version 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/Unicode4.1.0/">Unicode 4.1.0</a>.
3049 <dd>(<code><a href="http://www.unicode.org/versions/">http://www.unicode.org/versions/</a></code>)</dd>
3051 <dt>[XML10]
3052 <dd><a name="refsXML10"></a> Tim Bray, Jean Paoli, C. M. Sperberg-McQueen, Eve Maler, François Yergeau, editors; "<cite>Extensible Markup Language (XML) 1.0 (Third Edition)</cite>", W3C Recommendation, 4 February 2004
3055 <dt>[XMLNAMES]
3056 <dd><a name="refsXMLNAMES"></a> Tim Bray, Dave Hollander, Andrew Layman, editors; "<cite>Namespaces in XML</cite>", W3C Recommendation, 14 January 1999
3057 <dd>(<a href="http://www.w3.org/TR/REC-xml-names/"><code>http://www.w3.org/TR/REC-xml-names/</code></a>)
3059 <dt>[YACC]
3060 <dd><a name="refsYACC"></a> S. C. Johnson; "<cite>YACC — Yet another compiler compiler</cite>", Technical Report, Murray Hill, 1975
3062 </dl>
3063 </body>
3064 </html>