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64 <body>
66 <p><a href="http://www.w3.org/"><img height=48 alt=W3C src="http://www.w3.org/Icons/w3c_home" width=72></a>
72 <dl>
74 <dt>This version:
79 <dt>Latest version:
82 http://www.w3.org/TR/css3-selectors</a>
84 <dt>Previous version:
93 <dd class="vcard"><a lang="tr" class="url fn" href="http://www.tantek.com/">Tantek Çelik</a> (Invited Expert)
101 <dd class="vcard"><span class="fn">John Williams</span> (former editor, <span class="company"><a
104 </dl>
115 <a
117 <a
119 <a
121 use</a> rules apply.
125 </div>
130 tree. Selectors have been optimized for use with HTML and XML, and
131 are designed to be usable in performance-critical code.</p>
134 Style Sheets) is a language for describing the rendering of <acronym
137 screen, on paper, in speech, etc. CSS uses Selectors for binding
138 style properties to elements in the document. This document
139 describes extensions to the selectors defined in CSS level 2. These
140 extended selectors will be used by CSS level 3.
146 <p>That is, given an element and a selector, this specification
147 defines whether that element matches the selector.</p>
149 <p>These expressions can also be used, for instance, to select a set
150 of elements, or a single element from a set of elements, by
151 evaluating the expression across all the elements in a
158 <p><em>This section describes the status of this document at the
159 time of its publication. Other documents may supersede this
160 document. A list of current W3C publications and the latest revision
161 of this technical report can be found in the <a
163 http://www.w3.org/TR/.</a></em></p>
171 <p>The CSS Working Group doesn't expect that all implementations of
172 CSS3 will have to implement all selectors. Instead, there will
173 probably be a small number of variants of CSS3, called profiles. For
174 example, it may be that only a profile for interactive user agents
175 will include all of the selectors.</p>
180 document is a revision of the <a
183 implementation feedback received in the past few years. It is
184 expected that this last call will proceed straight to Proposed
185 Recommendation stage since it is believed that interoperability will
186 be demonstrable.</p>
188 <p>All persons are encouraged to review and implement this
189 specification and return comments to the (<a
191 public mailing list <a
194 Members can also send comments directly to the CSS Working
195 Group.
198 <p>This is still a draft document and may be updated, replaced, or
199 obsoleted by other documents at any time. It is inappropriate to
204 The English version of this specification is the only normative
205 version.
213 <ul>
217 </ul>
227 </ul>
229 <ul>
231 </ul>
234 <li class="tocline4"><a href="#attribute-representation">6.3.1. Representation of attributes and attributes values</a>
238 </ul>
248 <ul>
261 </ul>
263 </ul>
264 </li>
265 </ul>
267 <ul>
272 </ul>
279 <li class="tocline4"><a href="#adjacent-sibling-combinators">8.3.1. Adjacent sibling combinator</a>
280 <li class="tocline4"><a href="#general-sibling-combinators">8.3.2. General sibling combinator</a></li>
281 </ul>
282 </li>
283 </ul>
289 </ul>
296 </ul>
298 </div>
304 <p>Some features of this specification are specific to CSS, or have
305 particular limitations or rules specific to CSS. In this
306 specification, these have been described in terms of CSS2.1. <a
311 <p>All of the text of this specification is normative except
312 examples, notes, and sections explicitly marked as
313 non-normative.</p>
319 <p>The main differences between the selectors in CSS2 and those in
320 Selectors are:
322 <ul>
324 <li>the list of basic definitions (selector, group of selectors,
325 simple selector, etc.) has been changed; in particular, what was
326 referred to in CSS2 as a simple selector is now called a sequence
327 of simple selectors, and the term "simple selector" is now used for
328 the components of this sequence</li>
330 <li>an optional namespace component is now allowed in type element
331 selectors, the universal selector and attribute selectors</li>
335 <li>new simple selectors including substring matching attribute
336 selectors, and new pseudo-classes</li>
339 for pseudo-elements</li>
343 <li>profiles to be added to specifications integrating Selectors
344 and defining the set of selectors which is actually supported by
345 each specification</li>
347 <li>Selectors are now a CSS3 Module and an independent
348 specification; other specifications can now refer to this document
349 independently of CSS</li>
353 </ul>
357 <p><em>This section is non-normative, as it merely summarizes the
358 following sections.</em></p>
360 <p>A Selector represents a structure. This structure can be used as a
361 condition (e.g. in a CSS rule) that determines which elements a
362 selector matches in the document tree, or as a flat description of the
363 HTML or XML fragment corresponding to that structure.</p>
365 <p>Selectors may range from simple element names to rich contextual
366 representations.</p>
371 <thead>
372 <tr>
377 <tbody>
378 <tr>
383 selector</a></td>
385 <tr>
391 <tr>
396 selectors</a></td>
398 <tr>
404 selectors</a></td>
406 <tr>
412 selectors</a></td>
414 <tr>
420 selectors</a></td>
422 <tr>
428 selectors</a></td>
430 <tr>
436 selectors</a></td>
438 <tr>
444 selectors</a></td>
446 <tr>
451 pseudo-classes</a></td>
453 <tr>
458 pseudo-classes</a></td>
460 <tr>
463 from the last one</td>
466 pseudo-classes</a></td>
468 <tr>
473 pseudo-classes</a></td>
475 <tr>
478 from the last one</td>
481 pseudo-classes</a></td>
483 <tr>
488 pseudo-classes</a></td>
490 <tr>
495 pseudo-classes</a></td>
497 <tr>
502 pseudo-classes</a></td>
504 <tr>
509 pseudo-classes</a></td>
511 <tr>
516 pseudo-classes</a></td>
518 <tr>
523 pseudo-classes</a></td>
525 <tr>
528 nodes)</td>
531 pseudo-classes</a></td>
533 <tr>
536 which the target is not yet visited (:link) or already visited
537 (:visited)</td>
540 pseudo-classes</a></td>
542 <tr>
547 action pseudo-classes</a></td>
549 <tr>
554 pseudo-class</a></td>
556 <tr>
559 language specifies how language is determined)</td>
562 pseudo-class</a></td>
564 <tr>
567 disabled</td>
570 pseudo-classes</a></td>
572 <tr>
578 pseudo-classes</a></td>
580 <tr>
585 pseudo-element</a></td>
587 <tr>
592 pseudo-element</a></td>
594 <tr>
597 selected/highlighted by the user</td>
600 fragments pseudo-elements</a></td>
602 <tr>
607 pseudo-element</a></td>
609 <tr>
614 pseudo-element</a></td>
616 <tr>
622 selectors</a></td>
624 <tr>
629 selectors</a></td>
631 <tr>
636 pseudo-class</a></td>
638 <tr>
643 combinator</a></td>
645 <tr>
650 combinator</a></td>
652 <tr>
658 <tr>
665 <p>The meaning of each selector is derived from the table above by
667 column.</p>
671 <p>The case sensitivity of document language element names, attribute
672 names, and attribute values in selectors depends on the document
673 language. For example, in HTML, element names are case-insensitive,
674 but in XML, they are case-sensitive.</p>
687 selector or universal selector is allowed in the sequence.</p>
699 sequence of simple selectors.</p>
704 space may appear between a combinator and the simple selectors around
709 never part of white space.</p>
711 <p>The elements of a document tree that are represented by a selector
713 selector consisting of a single sequence of simple selectors
714 represents any element satisfying its requirements. Prepending another
715 sequence of simple selectors and a combinator to a sequence imposes
716 additional matching constraints, so the subjects of a selector are
717 always a subset of the elements represented by the last sequence of
718 simple selectors.</p>
720 <p>An empty selector, containing no sequence of simple selectors and
726 <p>When several selectors share the same declarations, they may be
731 <p>In this example, we condense three rules with identical
732 declarations into one. Thus,</p>
733 <pre>h1 { font-family: sans-serif }
734 h2 { font-family: sans-serif }
735 h3 { font-family: sans-serif }</pre>
738 </div>
741 because all the selectors are valid selectors. If just one of these
742 selectors were invalid, the entire group of selectors would be
743 invalid. This would invalidate the rule for all three heading
744 elements, whereas in the former case only one of the three individual
745 heading rules would be invalidated.</p>
753 element type. A type selector represents an instance of the element
754 type in the document tree.</p>
760 </div>
767 that has been previously declared may be prepended to the element name
771 <p>The namespace component may be left empty to indicate that the
772 selector is only to represent elements with no declared namespace.</p>
774 <p>An asterisk may be used for the namespace prefix, indicating that
775 the selector represents elements in any namespace (including elements
776 with no namespace).</p>
778 <p>Element type selectors that have no namespace component (no
779 namespace separator), represent elements without regard to the
780 element's namespace (equivalent to "<code>*|</code>") unless a default
781 namespace has been declared. If a default namespace has been declared,
782 the selector will represent only elements in the default
783 namespace.</p>
785 <p>A type selector containing a namespace prefix that has not been
787 The mechanism for declaring a namespace prefix is left up to the
788 language implementing Selectors. In CSS, such a mechanism is defined
789 in the General Syntax module.</p>
791 <p>In a namespace-aware client, element type selectors will only match
792 against the <a
794 of the element's <a
797 behaviors in down-level clients.</p>
801 <dl>
805 <dd>elements with name E in any namespace, including those without any
806 declared namespace</dd>
810 <dd>if no default namespace has been specified, this is equivalent to *|E.
811 Otherwise it is equivalent to ns|E where ns is the default namespace.</dd>
812 </dl>
817 <pre>@namespace foo url(http://www.example.com);
818 foo|h1 { color: blue }
819 foo|* { color: yellow }
820 |h1 { color: red }
821 *|h1 { color: green }
822 h1 { color: green }</pre>
827 <p>The second rule will match all elements in the
831 any declared namespace.</p>
834 namespace (including those without any declared namespace).</p>
836 <p>The last rule is equivalent to the fourth rule because no default
837 namespace has been defined.</p>
839 </div>
845 type. It represents any single element in the document tree in any
846 namespace (including those without any declared namespace) if no
847 default namespace has been specified. If a default namespace has been
851 <p>If the universal selector is not the only component of a sequence
856 <ul>
860 </ul>
861 </div>
865 omitted.</p>
869 <p>The universal selector allows an optional namespace component. It
870 is used as follows:</p>
872 <dl>
880 <dd>if no default namespace has been specified, this is equivalent to *|*.
881 Otherwise it is equivalent to ns|* where ns is the default namespace.</dd>
882 </dl>
884 <p>A universal selector containing a namespace prefix that has not
886 selector. The mechanism for declaring a namespace prefix is left up
887 to the language implementing Selectors. In CSS, such a mechanism is
888 defined in the General Syntax module.</p>
893 <p>Selectors allow the representation of an element's attributes. When
894 a selector is used as an expression to match against an element,
895 attribute selectors must be considered to match an element if that
896 element has an attribute that matches the attribute represented by the
897 attribute selector.</p>
900 selectors</a></h4>
904 <dl>
907 the attribute.</dd>
916 spaces).</dd>
926 </dl>
928 <p>Attribute values must be identifiers or strings. The
929 case-sensitivity of attribute names and values in selectors depends on
930 the document language.</p>
938 value:</p>
942 <p>In the following example, the selector represents a
948 <p>Multiple attribute selectors can be used to represent several
949 attributes of an element, or several conditions on the same
958 and "~=". The first selector will represent, for example, the value
978 <p>Similarly, the following selectors represents a
982 <pre>DIALOGUE[character=romeo]
983 DIALOGUE[character=juliet]</pre>
985 </div>
988 selectors</h4>
990 <p>Three additional attribute selectors are provided for matching
991 substrings in the value of an attribute:</p>
993 <dl>
1003 </dl>
1005 <p>Attribute values must be identifiers or strings. The
1006 case-sensitivity of attribute names in selectors depends on the
1007 document language.</p>
1012 image:</p>
1020 </div>
1024 <p>Attribute selectors allow an optional namespace component to the
1025 attribute name. A namespace prefix that has been previously declared
1026 may be prepended to the attribute name separated by the namespace
1028 the Namespaces in the XML recommendation, default namespaces do not
1029 apply to attributes, therefore attribute selectors without a namespace
1030 component apply only to attributes that have no declared namespace
1031 (equivalent to "<code>|attr</code>"). An asterisk may be used for the
1032 namespace prefix indicating that the selector is to match all
1033 attribute names without regard to the attribute's namespace.
1035 <p>An attribute selector with an attribute name containing a namespace
1036 prefix that has not been previously declared is an <a
1038 a namespace prefix is left up to the language implementing Selectors.
1039 In CSS, such a mechanism is defined in the General Syntax module.
1044 [foo|att=val] { color: blue }
1045 [*|att] { color: yellow }
1046 [|att] { color: green }
1047 [att] { color: green }</pre>
1049 <p>The first rule will match only elements with the attribute
1053 <p>The second rule will match only elements with the attribute
1055 (including no declared namespace).</p>
1057 <p>The last two rules are equivalent and will match only elements
1059 declared to be in a namespace.</p>
1061 </div>
1065 <p>Attribute selectors represent explicitly set attribute values in
1066 the document tree. Default attribute values may be defined in a DTD or
1067 elsewhere, but cannot always be selected by attribute
1068 selectors. Selectors should be designed so that they work even if the
1069 default values are not included in the document tree.</p>
1078 knowledge of that namespace to treat default attribute values as if
1079 they were present in the document. (For example, an XHTML UA is not
1080 required to use its built-in knowledge of the XHTML DTD.)</p>
1083 choose to ignore external subsets.</p>
1095 <pre>EXAMPLE[notation=decimal] { /*... default property settings ...*/ }
1096 EXAMPLE[notation=octal] { /*... other settings...*/ }</pre>
1099 is set by default, i.e. not set explicitly. To catch all cases, the
1100 attribute selector for the default value must be dropped:</p>
1102 <pre>EXAMPLE { /*... default property settings ...*/ }
1103 EXAMPLE[notation=octal] { /*... other settings...*/ }</pre>
1106 more specific than the tag
1107 selector alone, the style declarations in the second rule will override
1108 those in the first for elements that have a "notation" attribute value
1109 of "octal". Care has to be taken that all property declarations that
1110 are to apply only to the default case are overridden in the non-default
1111 cases' style rules.</p>
1113 </div>
1121 the same meaning. The attribute value must immediately follow the
1124 <p>UAs may apply selectors using the period (.) notation in XML
1125 documents if the UA has namespace-specific knowledge that allows it to
1127 respective namespace. One such example of namespace-specific knowledge
1128 is the prose in the specification for a particular namespace (e.g. SVG
1139 <p>We can assign style information to all elements with
1148 <p>The following assigns style only to H1 elements with
1153 <p>Given these rules, the first H1 instance below would not have
1154 green text, while the second would:</p>
1159 </div>
1169 has been assigned a list of <a
1179 </div>
1182 power to the "class" attribute, authors could conceivably design their
1183 own "document language" based on elements with almost no associated
1184 presentation (such as DIV and SPAN in HTML) and assigning style
1185 information through the "class" attribute. Authors should avoid this
1186 practice since the structural elements of a document language often
1187 have recognized and accepted meanings and author-defined classes may
1188 not.</p>
1191 class attributes, their values must be concatenated with spaces
1192 between the values before searching for the class. As of this time the
1193 working group is not aware of any manner in which this situation can
1194 be reached, however, so this behavior is explicitly non-normative in
1195 this specification.</p>
1199 <p>Document languages may contain attributes that are declared to be
1200 of type ID. What makes attributes of type ID special is that no two
1201 such attributes can have the same value in a document, regardless of
1202 the type of the elements that carry them; whatever the document
1203 language, an ID typed attribute can be used to uniquely identify its
1204 element. In HTML all ID attributes are named "id"; XML applications
1205 may name ID attributes differently, but the same restriction
1206 applies.</p>
1208 <p>An ID-typed attribute of a document language allows authors to
1209 assign an identifier to one element instance in the document tree. W3C
1210 ID selectors represent an element instance based on its identifier. An
1213 identifier.</p>
1215 <p>Selectors does not specify how a UA knows the ID-typed attribute of
1216 an element. The UA may, e.g., read a document's DTD, have the
1217 information hard-coded or ask the user.
1224 <p>The following ID selector represents any element whose ID-typed
1227 <p>The following selector represents any element whose ID-typed
1230 </div>
1234 contains an element's IDs is contained in a DTD or a schema. When
1235 parsing XML, UAs do not always read the DTD, and thus may not know
1236 what the ID of an element is (though a UA may have namespace-specific
1237 knowledge that allows it to determine which attribute is the ID
1238 attribute for that namespace). If a style sheet designer knows or
1239 suspects that a UA may not know what the ID of an element is, he
1240 should use normal attribute selectors instead:
1244 <p>If an element has multiple ID attributes, all of them must be
1245 treated as IDs for that element for the purposes of the ID
1246 selector. Such a situation could be reached using mixtures of xml:id,
1247 DOM3 Core, XML DTDs, and namespace-specific knowledge.</p>
1251 <p>The pseudo-class concept is introduced to permit selection based on
1252 information that lies outside of the document tree or that cannot be
1253 expressed using the other simple selectors.</p>
1257 optionally by a value between parentheses.</p>
1259 <p>Pseudo-classes are allowed in all sequences of simple selectors
1260 contained in a selector. Pseudo-classes are allowed anywhere in
1261 sequences of simple selectors, after the leading type selector or
1262 universal selector (possibly omitted). Pseudo-class names are
1263 case-insensitive. Some pseudo-classes are mutually exclusive, while
1264 others can be applied simultaneously to the same
1265 element. Pseudo-classes may be dynamic, in the sense that an element
1266 may acquire or lose a pseudo-class while a user interacts with the
1267 document.</p>
1272 <p>Dynamic pseudo-classes classify elements on characteristics other
1273 than their name, attributes, or content, in principle characteristics
1274 that cannot be deduced from the document tree.</p>
1276 <p>Dynamic pseudo-classes do not appear in the document source or
1277 document tree.</p>
1282 <p>User agents commonly display unvisited links differently from
1283 previously visited ones. Selectors
1287 <ul>
1289 not yet been visited.</li>
1291 been visited by the user. </li>
1292 </ul>
1294 <p>After some amount of time, user agents may choose to return a
1295 visited link to the (unvisited) ':link' state.</p>
1303 <p>The following selector represents links carrying class
1308 </div>
1311 authors to abuse the :link and :visited pseudo-classes to determine
1312 which sites a user has visited without the user's consent.
1314 <p>UAs may therefore treat all links as unvisited links, or implement
1315 other measures to preserve the user's privacy while rendering visited
1316 and unvisited links differently.</p>
1319 :hover, :active, and :focus</a></h5>
1321 <p>Interactive user agents sometimes change the rendering in response
1322 to user actions. Selectors provides
1323 three pseudo-classes for the selection of an element the user is
1324 acting on.</p>
1326 <ul>
1329 designates an element with a pointing device, but does not activate
1330 it. For example, a visual user agent could apply this pseudo-class
1331 when the cursor (mouse pointer) hovers over a box generated by the
1332 element. User agents not that do not support <a
1334 media</a> do not have to support this pseudo-class. Some conforming
1335 user agents that support <a
1337 media</a> may not be able to support this pseudo-class (e.g., a pen
1338 device that does not detect hovering).</li>
1341 is being activated by the user. For example, between the times the
1342 user presses the mouse button and releases it.</li>
1345 has the focus (accepts keyboard or mouse events, or other forms of
1346 input). </li>
1348 </ul>
1350 <p>There may be document language or implementation specific limits on
1354 <p>These pseudo-classes are not mutually exclusive. An element may
1355 match several pseudo-classes at the same time.</p>
1357 <p>Selectors doesn't define if the parent of an element that is
1358 ':active' or ':hover' is also in that state.</p>
1362 <pre>a:link /* unvisited links */
1363 a:visited /* visited links */
1364 a:hover /* user hovers */
1365 a:active /* active links */</pre>
1367 <pre>a:focus
1368 a:focus:hover</pre>
1370 the pseudo-class :focus and in the pseudo-class :hover.</p>
1371 </div>
1374 and ':active' (or ':link' and ':active').</p>
1378 <p>Some URIs refer to a location within a resource. This kind of URI
1380 identifier (called the fragment identifier).</p>
1382 <p>URIs with fragment identifiers link to a certain element within the
1383 document, known as the target element. For instance, here is a URI
1385 document:</p>
1390 pseudo-class. If the document's URI has no fragment identifier, then
1391 the document has no target element.</p>
1398 URI.</p>
1399 </div>
1404 target element red and place an image before it, if there is one:</p>
1405 <pre>*:target { color : red }
1406 *:target::before { content : url(target.png) }</pre>
1407 </div>
1411 <p>If the document language specifies how the human language of an
1412 element is determined, it is possible to write selectors that
1413 represent an element based on its language. For example, in HTML <a
1416 element, and possibly by information from the protocol (such as HTTP
1418 there may be other document language-specific methods for determining
1419 the language.</p>
1422 is in language C. Whether an element is represented by a
1424 being either equal to, or a hyphen-separated substring of, the
1425 element's language value, in the same way as if performed by the <a
1427 selectors. The identifier C does not have to be a valid language
1428 name.</p>
1442 <p>The two following selectors represent an HTML document that is in
1443 Belgian, French, or German. The two next selectors represent
1445 or German.</p>
1446 <pre>html:lang(fr-be)
1447 html:lang(de)
1448 :lang(fr-be) > q
1450 </div>
1457 the look of user interface elements that are enabled — which the
1458 user can select or activate in some fashion (e.g. clicking on a button
1459 with a mouse). There is a need for such a pseudo-class because there
1460 is no way to programmatically specify the default appearance of say,
1462 would look like when it was disabled.</p>
1465 author to specify precisely how a disabled or inactive user interface
1466 element should look.</p>
1468 <p>Most elements will be neither enabled nor disabled. An element is
1469 enabled if the user can either activate it or transfer the focus to
1470 it. An element is disabled if it could be enabled, but the user cannot
1471 presently activate it or transfer focus to it.</p>
1476 <p>Radio and checkbox elements can be toggled by the user. Some menu
1477 items are "checked" when the user selects them. When such elements are
1481 attributes as described in <a
1486 in nature, and is altered by user action, since it can also be based
1495 <p>Radio and checkbox elements can be toggled by the user, but are
1496 sometimes in an indeterminate state, neither checked nor unchecked.
1497 This can be due to an element attribute, or DOM manipulation.</p>
1499 <p>A future version of this specification may introduce an
1501 <!--While the <code>:indeterminate</code> pseudo-class is dynamic in
1502 nature, and is altered by user action, since it can also be based on
1503 the presence of an element attribute, it applies to all media.</p>
1505 <p>Components of a radio-group initialized with no pre-selected choice
1508 </div>
1514 pseudo-classes</dfn> to permit selection based on extra information that lies in
1515 the document tree but cannot be represented by other simple selectors or
1516 combinators.
1518 <p>Note that standalone pieces of PCDATA (text nodes in the DOM) are
1519 not counted when calculating the position of an element in the list of
1520 children of its parent. When calculating the position of an element in
1521 the list of children of its parent, the index numbering starts at 1.
1527 the root of the document. In HTML 4, this is always the
1533 <p>The
1535 pseudo-class notation represents an element that has
1541 each. For example, this allows the selectors to address every other
1542 row in a table, and could be used to alternate the color
1545 integers. The index of the first child of an element is 1.
1556 tr:nth-child(odd) /* same */
1557 tr:nth-child(2n) /* represents every even row of an HTML table */
1558 tr:nth-child(even) /* same */
1560 /* Alternate paragraph colours in CSS */
1565 </div>
1570 included, so the syntax simplifies to
1578 </div>
1586 bar:nth-child(n+0) /* same */
1587 bar:nth-child(n) /* same */
1589 </div>
1598 </div>
1601 pseudo-class represents no element in the document tree.</p>
1606 tree.</p>
1611 </div>
1614 expression must be removed (it is effectively replaced by the "-"
1622 </div>
1628 pseudo-class notation represents an element that has
1634 as arguments.
1641 foo:nth-last-child(odd) /* represents all odd foo elements in their parent element,
1642 counting from the last one */</pre>
1643 </div>
1649 pseudo-class notation represents an element that has
1654 of that type after all the children of that type have been split into
1656 for the syntax of its argument. It also accepts the
1665 </div>
1671 pseudo-class notation represents an element that has
1683 following selector:</p>
1686 selector ends up being just as long:</p>
1688 </div>
1694 represents an element that is the first child of some other element.
1708 fragment:
1716 a:first-child /* Same (assuming a is not the root element) */</pre>
1717 </div>
1722 represents an element that is the last child of some other element.
1729 </div>
1734 represents an element that is the first sibling of its type in the list of
1735 children of its parent element.
1739 <p>The following selector represents a definition title
1742 its parent element.</p>
1745 elements in the following example but not for the third one:</p>
1757 </div>
1763 the last sibling of its type in the list of children of its parent
1764 element.</p>
1768 <p>The following selector represents the last data cell
1771 </div>
1775 <p>Represents an element that has a parent element and whose parent
1776 element has no other element children. Same as
1779 specificity.</p>
1783 <p>Represents an element that has a parent element and whose parent
1784 element has no other element children with the same element name. Same
1787 specificity.</p>
1793 no children at all. In terms of the DOM, only element nodes and text
1794 nodes (including CDATA nodes and entity references) whose data has a
1795 non-zero length must be considered as affecting emptiness; comments,
1796 PIs, and other nodes must not affect whether an element is considered
1797 empty or not.</p>
1804 following fragments:</p>
1808 </div>
1810 <h4><a name=content-selectors>6.6.6. Blank</a></h4> <!-- It's the Return of Appendix H!!! Run away! -->
1813 <!-- (used to be :contains()) -->
1819 selector</a> (excluding the negation pseudo-class itself and
1820 pseudo-elements) as an argument. It represents an element that is not
1821 represented by the argument.
1823 <!-- pseudo-elements are not simple selectors, so the above paragraph
1824 may be a bit confusing -->
1829 elements in an HTML document that are not disabled.</p>
1832 elements.</p>
1834 <p>The following group of selectors represents all HTML elements
1835 except links.</p>
1837 </div>
1839 <p>Default namespace declarations do not affect the argument of the
1840 negation pseudo-class unless the argument is a universal selector or a
1841 type selector.</p>
1845 <p>Assuming that the default namespace is bound to
1846 "http://example.com/", the following selector represents all
1847 elements that are not in that namespace:</p>
1849 <p>The following CSS selector matches any element being hovered,
1850 regardless of its namespace. In particular, it is not limited to
1851 only matching elements in the default namespace that are not being
1852 hovered, and elements not in the default namespace don't match the
1855 </div>
1861 specificity.</p>
1865 <p>Pseudo-elements create abstractions about the document tree beyond
1866 those specified by the document language. For instance, document
1867 languages do not offer mechanisms to access the first letter or first
1868 line of an element's content. Pseudo-elements allow designers to refer
1869 to this otherwise inaccessible information. Pseudo-elements may also
1870 provide designers a way to refer to content that does not exist in the
1873 content).</p>
1876 by the name of the pseudo-element.</p>
1879 in order to establish a discrimination between pseudo-classes and
1880 pseudo-elements. For compatibility with existing style sheets, user
1881 agents must also accept the previous one-colon notation for
1887 <p>Only one pseudo-element may appear per selector, and if present it
1888 must appear after the sequence of simple selectors that represents the
1890 future version of this specification may allow multiple
1891 pesudo-elements per selector.</span></p>
1896 of the first formatted line of an element.
1903 </div>
1906 HTML element. It does match a pseudo-element that conforming user
1907 agents will insert at the beginning of every paragraph.</p>
1909 <p>Note that the length of the first line depends on a number of
1910 factors, including the width of the page, the font size, etc. Thus,
1911 an ordinary HTML paragraph such as:</p>
1913 <pre>
1915 paragraph that will be broken into several
1916 lines. The first line will be identified
1917 by a fictional tag sequence. The other lines
1918 will be treated as ordinary lines in the
1920 </pre>
1922 <p>the lines of which happen to be broken as follows:
1924 <pre>
1925 THIS IS A SOMEWHAT LONG HTML PARAGRAPH THAT
1926 will be broken into several lines. The first
1927 line will be identified by a fictional tag
1928 sequence. The other lines will be treated as
1929 ordinary lines in the paragraph.
1930 </pre>
1934 fictional tag sequence helps to show how properties are inherited.</p>
1936 <pre>
1939 lines. The first line will be identified
1940 by a fictional tag sequence. The other lines
1941 will be treated as ordinary lines in the
1943 </pre>
1945 <p>If a pseudo-element breaks up a real element, the desired effect
1946 can often be described by a fictional tag sequence that closes and
1947 then re-opens the element. Thus, if we mark up the previous paragraph
1950 <pre>
1952 paragraph that will be broken into several
1954 by a fictional tag sequence. The other lines
1955 will be treated as ordinary lines in the
1957 </pre>
1959 <p>the user agent could simulate start and end tags for
1963 <pre>
1965 somewhat long HTML
1966 paragraph that will <b></SPAN></b></P::first-line><b><SPAN class="test"></b> be
1967 broken into several
1969 by a fictional tag sequence. The other lines
1970 will be treated as ordinary lines in the
1972 </pre>
1975 attached to a block-level element, an inline-block, a table-caption,
1976 or a table-cell.</p>
1979 element may occur inside a
1980 block-level descendant in the same flow (i.e., a block-level
1981 descendant that is not positioned and not a float). E.g., the first
1986 <p>The first line of a table-cell or inline-block cannot be the first
1997 <p>A UA should act as if the fictional start tags of the
1999 innermost enclosing block-level element. (Since CSS1 and CSS2 were
2000 silent on this case, authors should not rely on this behavior.) Here
2001 is an example. The fictional tag sequence for</p>
2003 <pre>
2008 </pre>
2012 <pre>
2014 <P><DIV::first-line><P::first-line>First paragraph</P::first-line></DIV::first-line></P>
2017 </pre>
2020 inline-level element, but with certain restrictions. In CSS, the
2022 pseudo-element: font properties, color property, background
2023 properties, 'word-spacing', 'letter-spacing', 'text-decoration',
2024 'vertical-align', 'text-transform', 'line-height'. UAs may apply other
2025 properties as well.</p>
2031 letter of the first line of a block, if it is not preceded by any
2032 other content (such as images or inline tables) on its line. The
2034 caps", which are common typographical effects. This type of initial
2035 letter is similar to an inline-level element if its 'float' property
2036 is 'none'; otherwise, it is similar to a floated element.</p>
2039 pseudo-elements: font properties, 'text-decoration', 'text-transform',
2040 'letter-spacing', 'word-spacing' (when appropriate), 'line-height',
2041 'float', 'vertical-align' (only if 'float' is 'none'), margin
2042 properties, padding properties, border properties, color property,
2043 background properties. UAs may apply other properties as well. To
2044 allow UAs to render a typographically correct drop cap or initial cap,
2045 the UA may choose a line-height, width and height based on the shape
2046 of the letter, unlike for normal elements.</p>
2050 <p>This example shows a possible rendering of an initial cap. Note
2052 pseudo-element is 1.1, but the UA in this example has computed the
2053 height of the first letter differently, so that it doesn't cause any
2054 unnecessary space between the first two lines. Also note that the
2057 <pre>
2058 p { line-height: 1.1 }
2059 p::first-letter { font-size: 3em; font-weight: normal }
2060 span { font-weight: bold }
2061 ...
2065 En dagelix geschrey de bange stad ontzet.
2066 </pre>
2069 </div>
2070 </div>
2075 <pre>
2082 P::first-letter { font-size: 200%; font-weight: bold; float: left }
2083 SPAN { text-transform: uppercase }
2091 </pre>
2096 <P><img src="first-letter.gif" alt="Image illustrating the combined effect of the ::first-letter and ::first-line pseudo-elements"></p>
2097 </div>
2102 <pre>
2106 T
2109 few words of an article in the Economist.
2111 </pre>
2114 the content (i.e., the initial character), while the ::first-line
2115 pseudo-element start tag is inserted right after the start tag of the
2116 block element.</p> </div>
2118 <p>In order to achieve traditional drop caps formatting, user agents
2119 may approximate font sizes, for example to align baselines. Also, the
2120 glyph outline may be taken into account when formatting.</p>
2124 punctuation classes), that precedes or follows the first letter should
2130 </div>
2137 block, list-item, table-cell, table-caption, and inline-block
2139 may allow this pesudo-element to apply to more element
2140 types.</span></p>
2143 such elements that contain text, or that have a descendant in the same
2144 flow that contains text. A UA should act as if the fictional start tag
2145 of the ::first-letter pseudo-element is just before the first text of
2146 the element, even if that first text is in a descendant.</p>
2150 <p>The fictional tag sequence for this HTMLfragment:
2153 <p>is:
2156 </div>
2158 <p>The first letter of a table-cell or inline-block cannot be the
2171 <p>In CSS, if an element is a list item ('display: list-item'), the
2173 principal box after the marker. UAs may ignore
2183 </div>
2185 <p>Some languages may have specific rules about how to treat certain
2186 letter combinations. In Dutch, for example, if the letter combination
2187 "ij" appears at the beginning of a word, both letters should be
2190 <p>If the letters that would form the ::first-letter are not in the
2192 may create a ::first-letter pseudo-element from one of the elements,
2193 both elements, or simply not create a pseudo-element.</p>
2195 <p>Similarly, if the first letter(s) of the block are not at the start
2196 of the line (for example due to bidirectional reordering), then the UA
2197 need not create the pseudo-element(s).
2202 how overlapping pseudo-elements may interact. The first letter of
2203 each P element will be green with a font size of '24pt'. The rest of
2204 the first formatted line will be 'blue' while the rest of the
2205 paragraph will be 'red'.</p>
2208 p::first-letter { color: green; font-size: 200% }
2209 p::first-line { color: blue }
2220 S
2223 ends up on two lines
2230 </div>
2236 of a document that has been highlighted by the user. This also
2237 applies, for example, to selected text within an editable text
2238 field. This pseudo-element should not be confused with the <code><a
2243 nature, and is altered by user action, it is reasonable to expect that
2244 when a UA re-renders to a static medium (such as a printed page, see
2246 dynamic medium (like screen), the UA may wish to transfer the current
2248 appropriate formatting and rendering take effect as well. This is not
2250 pseudo-element for static media.
2253 pseudo-elements: color, background, cursor (optional), outline
2254 (optional). The computed value of the 'background-image' property on
2261 can be used to describe generated content before or after an element's
2268 element including the inserted text.</p>
2274 <p>At times, authors may want selectors to describe an element that is
2275 the descendant of another element in the document tree (e.g., "an
2276 <code>EM</code> element that is contained within an <code>H1</code>
2277 element"). Descendant combinators express such a relationship. A
2279 separates two sequences of simple selectors. A selector of the form
2289 description of the following fragment:</p>
2296 either side of the "*" is not part of the universal selector; the
2297 whitespace is a combinator indicating that the DIV must be the
2298 ancestor of some element, and that that element must be an ancestor
2299 of the P.</p>
2300 <p>The following selector, which combines descendant combinators and
2305 </div>
2310 between two elements. A child combinator is made of the
2312 separates two sequences of simple selectors.
2320 <p>The following example combines descendant combinators and child
2321 combinators.</p>
2328 </div>
2330 <p>For information on selecting the first child of an element, please
2331 see the section on the <code><a
2333 above.</p>
2337 <p>There are two different sibling combinators: the adjacent sibling
2338 combinator and the general sibling combinator. In both cases,
2339 non-element nodes (e.g. text between elements) are ignored when
2340 considering adjacency of elements.</p>
2346 sequences of simple selectors. The elements represented by the two
2347 sequences share the same parent in the document tree and the element
2348 represented by the first sequence immediately precedes the element
2349 represented by the second one.</p>
2356 <p>The following selector is conceptually similar to the one in the
2357 previous example, except that it adds an attribute selector — it
2361 </div>
2368 simple selectors. The elements represented by the two sequences share
2369 the same parent in the document tree and the element represented by
2370 the first sequence precedes (not necessarily immediately) the element
2371 represented by the second one.</p>
2377 is a correct and valid, but partial, description of:</p>
2381 </div>
2387 <ul>
2389 <li>count the number of class selectors, attributes selectors, and pseudo-classes in the selector (= b)</li>
2392 </ul>
2395 are counted like any other, but the negation itself does not count as
2396 a pseudo-class.</p>
2398 <p>Concatenating the three numbers a-b-c (in a number system with a
2399 large base) gives the specificity.</p>
2412 </pre>
2413 </div>
2423 <p>The grammar below defines the syntax of Selectors. It is globally
2425 it directly, since it doesn't express the parsing conventions). The
2426 format of the productions is optimized for human consumption and some
2428 are used:</p>
2430 <ul>
2436 </ul>
2440 <pre>selectors_group
2441 : selector [ COMMA S* selector ]*
2442 ;
2444 selector
2445 : simple_selector_sequence [ combinator simple_selector_sequence ]*
2446 ;
2448 combinator
2449 /* combinators can be surrounded by white space */
2450 : PLUS S* | GREATER S* | TILDE S* | S+
2451 ;
2453 simple_selector_sequence
2454 : [ type_selector | universal ]
2455 [ HASH | class | attrib | pseudo | negation ]*
2456 | [ HASH | class | attrib | pseudo | negation ]+
2457 ;
2459 type_selector
2460 : [ namespace_prefix ]? element_name
2461 ;
2463 namespace_prefix
2464 : [ IDENT | '*' ]? '|'
2465 ;
2467 element_name
2468 : IDENT
2469 ;
2471 universal
2472 : [ namespace_prefix ]? '*'
2473 ;
2475 class
2476 : '.' IDENT
2477 ;
2479 attrib
2480 : '[' S* [ namespace_prefix ]? IDENT S*
2481 [ [ PREFIXMATCH |
2482 SUFFIXMATCH |
2483 SUBSTRINGMATCH |
2484 '=' |
2485 INCLUDES |
2486 DASHMATCH ] S* [ IDENT | STRING ] S*
2487 ]? ']'
2488 ;
2490 pseudo
2491 /* '::' starts a pseudo-element, ':' a pseudo-class */
2492 /* Exceptions: :first-line, :first-letter, :before and :after. */
2493 /* Note that pseudo-elements are restricted to one per selector and */
2494 /* occur only in the last simple_selector_sequence. */
2495 : ':' ':'? [ IDENT | functional_pseudo ]
2496 ;
2498 functional_pseudo
2499 : FUNCTION S* expression ')'
2500 ;
2502 expression
2503 /* In CSS3, the expressions are identifiers, strings, */
2504 /* or of the form "an+b" */
2505 : [ [ PLUS | '-' | DIMENSION | NUMBER | STRING | IDENT ] S* ]+
2506 ;
2508 negation
2509 : NOT S* negation_arg S* ')'
2510 ;
2512 negation_arg
2513 : type_selector | universal | HASH | class | attrib | pseudo
2514 ;</pre>
2521 case-insensitive.</p>
2524 number that current versions of Flex can deal with (decimal 255). They
2529 <pre>%option case-insensitive
2531 ident [-]?{nmstart}{nmchar}*
2532 name {nmchar}+
2533 nmstart [_a-z]|{nonascii}|{escape}
2536 escape {unicode}|\\[^\n\r\f0-9a-f]
2537 nmchar [_a-z0-9-]|{nonascii}|{escape}
2539 string {string1}|{string2}
2541 string2 \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*\'
2542 invalid {invalid1}|{invalid2}
2544 invalid2 \'([^\n\r\f\\']|\\{nl}|{nonascii}|{escape})*
2545 nl \n|\r\n|\r|\f
2546 w [ \t\r\n\f]*
2548 %%
2550 [ \t\r\n\f]+ return S;
2557 {ident} return IDENT;
2558 {string} return STRING;
2560 {num} return NUMBER;
2567 @{ident} return ATKEYWORD;
2568 {invalid} return INVALID;
2569 {num}% return PERCENTAGE;
2570 {num}{ident} return DIMENSION;
2576 U\+[0-9a-f?]{1,6}(-[0-9a-f]{1,6})? return UNICODE_RANGE;
2578 \/\*[^*]*\*+([^/*][^*]*\*+)*\/ /* ignore comments */
2580 . return *yytext;</pre>
2584 <h2><a name=downlevel>11. Namespaces and down-level clients</a></h2>
2586 <p>An important issue is the interaction of CSS selectors with XML
2587 documents in web clients that were produced prior to this
2588 document. Unfortunately, due to the fact that namespaces must be
2589 matched based on the URI which identifies the namespace, not the
2590 namespace prefix, some mechanism is required to identify namespaces in
2591 CSS by their URI as well. Without such a mechanism, it is impossible
2592 to construct a CSS style sheet which will properly match selectors in
2593 all cases against a random set of XML documents. However, given
2594 complete knowledge of the XML document to which a style sheet is to be
2595 applied, and a limited use of namespaces within the XML document, it
2596 is possible to construct a style sheet in which selectors would match
2597 elements and attributes correctly.</p>
2599 <p>It should be noted that a down-level CSS client will (if it
2600 properly conforms to CSS forward compatible parsing rules) ignore all
2601 <code>@namespace</code> at-rules, as well as all style rules that make
2602 use of namespace qualified element type or attribute selectors. The
2603 syntax of delimiting namespace prefixes in CSS was deliberately chosen
2604 so that down-level CSS clients would ignore the style rules rather
2605 than possibly match them incorrectly.</p>
2607 <p>The use of default namespaces in CSS makes it possible to write
2608 element type selectors that will function in both namespace aware CSS
2609 clients as well as down-level clients. It should be noted that
2610 down-level clients may incorrectly match selectors against XML
2611 elements in other namespaces.</p>
2613 <p>The following are scenarios and examples in which it is possible to
2614 construct style sheets which would function properly in web clients
2615 that do not implement this proposal.</p>
2617 <ol>
2618 <li>
2620 <p>The XML document does not use namespaces.</p>
2622 <ul>
2624 <li>In this case, it is obviously not necessary to declare or use
2625 namespaces in the style sheet. Standard CSS element type and
2626 attribute selectors will function adequately in a down-level
2627 client.</li>
2629 <li>In a CSS namespace aware client, the default behavior of
2630 element selectors matching without regard to namespace will
2631 function properly against all elements, since no namespaces are
2632 present. However, the use of specific element type selectors that
2634 will guarantee that selectors will match only XML elements that do
2635 not have a declared namespace. </li>
2637 </ul>
2639 </li>
2641 <li>
2643 <p>The XML document defines a single, default namespace used
2644 throughout the document. No namespace prefixes are used in element
2645 names.</p>
2647 <ul>
2649 <li>In this case, a down-level client will function as if
2650 namespaces were not used in the XML document at all. Standard CSS
2651 element type and attribute selectors will match against all
2652 elements. </li>
2654 </ul>
2656 </li>
2658 <li>
2660 <p>The XML document does <b>not</b> use a default namespace, all
2661 namespace prefixes used are known to the style sheet author, and
2662 there is a direct mapping between namespace prefixes and namespace
2663 URIs. (A given prefix may only be mapped to one namespace URI
2664 throughout the XML document; there may be multiple prefixes mapped
2665 to the same URI).</p>
2667 <ul>
2669 <li>In this case, the down-level client will view and match
2670 element type and attribute selectors based on their fully
2671 qualified name, not the local part as outlined in the <a
2674 to describe the fully qualified names, e.g.
2676 <code><html:h1></code>. Selectors using the qualified name
2677 will only match XML elements that use the same prefix. Other
2678 namespace prefixes used in the XML that are mapped to the same URI
2679 will not match as expected unless additional CSS style rules are
2680 declared for them.</li>
2682 <li>Note that selectors declared in this fashion will
2683 <em>only</em> match in down-level clients. A CSS namespace aware
2684 client will match element type and attribute selectors based on
2685 the name's local part. Selectors declared with the fully
2686 qualified name will not match (unless there is no namespace prefix
2687 in the fully qualified name).</li>
2689 </ul>
2691 </li>
2693 </ol>
2695 <p>In other scenarios: when the namespace prefixes used in the XML are
2696 not known in advance by the style sheet author; or a combination of
2697 elements with no namespace are used in conjunction with elements using
2698 a default namespace; or the same namespace prefix is mapped to
2699 <em>different</em> namespace URIs within the same document, or in
2700 different documents; it is impossible to construct a CSS style sheet
2701 that will function properly against all elements in those documents,
2702 unless, the style sheet is written using a namespace URI syntax (as
2703 outlined in this document or similar) and the document is processed by
2704 a CSS and XML namespace aware client.</p>
2706 <h2><a name=profiling>12. Profiles</a></h2>
2708 <p>Each specification using Selectors must define the subset of W3C
2709 Selectors it allows and excludes, and describe the local meaning of
2710 all the components of that subset.</p>
2712 <p>Non normative examples:
2716 <tbody>
2717 <tr>
2719 <tr>
2720 <th>Specification</th>
2721 <td>CSS level 1</td></tr>
2722 <tr>
2723 <th>Accepts</th>
2724 <td>type selectors<br>class selectors<br>ID selectors<br>:link,
2725 :visited and :active pseudo-classes<br>descendant combinator
2726 <br>::first-line and ::first-letter pseudo-elements</td></tr>
2727 <tr>
2728 <th>Excludes</th>
2729 <td>
2731 <p>universal selector<br>attribute selectors<br>:hover and :focus
2732 pseudo-classes<br>:target pseudo-class<br>:lang() pseudo-class<br>all UI
2733 element states pseudo-classes<br>all structural
2734 pseudo-classes<br>negation pseudo-class<br>all
2735 UI element fragments pseudo-elements<br>::before and ::after
2736 pseudo-elements<br>child combinators<br>sibling combinators
2738 <p>namespaces</td></tr>
2739 <tr>
2740 <th>Extra constraints</th>
2741 <td>only one class selector allowed per sequence of simple
2742 selectors</td></tr></tbody></table><br><br>
2744 <tbody>
2745 <tr>
2747 <tr>
2748 <th>Specification</th>
2749 <td>CSS level 2</td></tr>
2750 <tr>
2751 <th>Accepts</th>
2752 <td>type selectors<br>universal selector<br>attribute presence and
2753 values selectors<br>class selectors<br>ID selectors<br>:link, :visited,
2754 :active, :hover, :focus, :lang() and :first-child pseudo-classes
2755 <br>descendant combinator<br>child combinator<br>adjacent sibling
2756 combinator<br>::first-line and ::first-letter pseudo-elements<br>::before
2757 and ::after pseudo-elements</td></tr>
2758 <tr>
2759 <th>Excludes</th>
2760 <td>
2762 <p>content selectors<br>substring matching attribute
2763 selectors<br>:target pseudo-classes<br>all UI element
2764 states pseudo-classes<br>all structural pseudo-classes other
2765 than :first-child<br>negation pseudo-class<br>all UI element
2766 fragments pseudo-elements<br>general sibling combinators
2768 <p>namespaces</td></tr>
2769 <tr>
2770 <th>Extra constraints</th>
2771 <td>more than one class selector per sequence of simple selectors (CSS1
2772 constraint) allowed</td></tr></tbody></table>
2774 <p>In CSS, selectors express pattern matching rules that determine which style
2775 rules apply to elements in the document tree.
2777 <p>The following selector (CSS level 2) will <b>match</b> all anchors <code>a</code>
2778 with attribute <code>name</code> set inside a section 1 header <code>h1</code>:
2779 <pre>h1 a[name]</pre>
2781 <p>All CSS declarations attached to such a selector are applied to elements
2782 matching it. </div>
2786 <tbody>
2787 <tr>
2789 <tr>
2790 <th>Specification</th>
2791 <td>STTS 3</td>
2792 </tr>
2793 <tr>
2794 <th>Accepts</th>
2795 <td>
2797 <p>type selectors<br>universal selectors<br>attribute selectors<br>class
2798 selectors<br>ID selectors<br>all structural pseudo-classes<br>
2799 all combinators
2801 <p>namespaces</td></tr>
2802 <tr>
2803 <th>Excludes</th>
2804 <td>non-accepted pseudo-classes<br>pseudo-elements<br></td></tr>
2805 <tr>
2806 <th>Extra constraints</th>
2807 <td>some selectors and combinators are not allowed in fragment
2808 descriptions on the right side of STTS declarations.</td></tr></tbody></table>
2809 <form>
2835 </form>
2837 <p>Selectors can be used in STTS 3 in two different
2838 manners:
2839 <ol>
2840 <li>a selection mechanism equivalent to CSS selection mechanism: declarations
2841 attached to a given selector are applied to elements matching that selector,
2842 <li>fragment descriptions that appear on the right side of declarations.
2843 </li></ol></div>
2845 <h2><a name=Conformance></a>13. Conformance and requirements</h2>
2847 <p>This section defines conformance with the present specification only.
2849 <p>The inability of a user agent to implement part of this specification due to
2850 the limitations of a particular device (e.g., non interactive user agents will
2851 probably not implement dynamic pseudo-classes because they make no sense without
2852 interactivity) does not imply non-conformance.
2854 <p>All specifications reusing Selectors must contain a <a
2856 subset of Selectors it accepts or excludes, and describing the constraints
2857 it adds to the current specification.
2859 <p>Invalidity is caused by a parsing error, e.g. an unrecognized token or a token
2860 which is not allowed at the current parsing point.
2862 <p>User agents must observe the rules for handling parsing errors:
2863 <ul>
2864 <li>a simple selector containing an undeclared namespace prefix is invalid</li>
2865 <li>a selector containing an invalid simple selector, an invalid combinator
2866 or an invalid token is invalid. </li>
2867 <li>a group of selectors containing an invalid selector is invalid.</li>
2868 </ul>
2871 errors. (In the case of CSS, the entire rule in which the selector is
2872 used is dropped.)</p>
2874 <!-- Apparently all these references are out of date:
2875 <p>Implementations of this specification must behave as
2877 when parsing selectors and attempting matches. (In particular,
2878 implementations must assume the data is normalized and must not
2879 normalize it.) Normative rules for matching strings are defined in
2882 specification.</p>-->
2884 <h2><a name=Tests></a>14. Tests</h2>
2886 <p>This specification has <a
2888 suite</a> allowing user agents to verify their basic conformance to
2889 the specification. This test suite does not pretend to be exhaustive
2890 and does not cover all possible combined cases of Selectors.</p>
2892 <h2><a name=ACKS></a>15. Acknowledgements</h2>
2894 <p>The CSS working group would like to thank everyone who has sent
2895 comments on this specification over the years.</p>
2897 <p>The working group would like to extend special thanks to Donna
2898 McManus, Justin Baker, Joel Sklar, and Molly Ives Brower who perfermed
2899 the final editorial review.</p>
2901 <h2><a name=references>16. References</a></h2>
2905 <dt>[CSS1]
2906 <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
2909 <dt>[CSS21]
2910 <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
2913 <dt>[CWWW]
2914 <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
2917 <dt>[FLEX]
2918 <dd><a name="refsFLEX"></a> "<cite>Flex: The Lexical Scanner Generator</cite>", Version 2.3.7, ISBN 1882114213
2920 <dt>[HTML4]
2921 <dd><a name="refsHTML4"></a> Dave Ragget, Arnaud Le Hors, Ian Jacobs, editors; "<cite>HTML 4.01 Specification</cite>", W3C Recommendation, 24 December 1999
2924 <dt>[MATH]
2925 <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
2926 <dd>(<code><a href="http://www.w3.org/TR/REC-MathML/">http://www.w3.org/TR/REC-MathML/</a></code>)
2928 <dt>[RFC3066]
2929 <dd><a name="refsRFC3066"></a> H. Alvestrand; "<cite>Tags for the Identification of Languages</cite>", Request for Comments 3066, January 2001
2930 <dd>(<a href="http://www.ietf.org/rfc/rfc3066.txt"><code>http://www.ietf.org/rfc/rfc3066.txt</code></a>)
2932 <dt>[STTS]
2933 <dd><a name=refsSTTS></a> Daniel Glazman; "<cite>Simple Tree Transformation Sheets 3</cite>", Electricité de France, submission to the W3C, 11 November 1998
2934 <dd>(<code><a href="http://www.w3.org/TR/NOTE-STTS3">http://www.w3.org/TR/NOTE-STTS3</a></code>)
2936 <dt>[SVG]
2937 <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
2940 <dt>[UNICODE]</dt>
2942 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>.
2943 <dd>(<code><a href="http://www.unicode.org/versions/">http://www.unicode.org/versions/</a></code>)</dd>
2945 <dt>[XML10]
2946 <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
2949 <dt>[XMLNAMES]
2950 <dd><a name="refsXMLNAMES"></a> Tim Bray, Dave Hollander, Andrew Layman, editors; "<cite>Namespaces in XML</cite>", W3C Recommendation, 14 January 1999
2951 <dd>(<a href="http://www.w3.org/TR/REC-xml-names/"><code>http://www.w3.org/TR/REC-xml-names/</code></a>)
2953 <dt>[YACC]
2954 <dd><a name="refsYACC"></a> S. C. Johnson; "<cite>YACC — Yet another compiler compiler</cite>", Technical Report, Murray Hill, 1975
2956 </dl>
2957 </body>
2958 </html>