id Attribute
Where to use the id Attribute
id is a Common Attribute from the
Core Attribute Collection
and is of Type ID.
It may be used on most elements in the Element Index - all except: base, head, html, meta, title. It is #REQUIRED on the map element.
Note: Although the id attribute is seemingly permitted by the
*XHTML 1.1
Structure Module DTD on the
html and head elements,
its presence on these elements currently
causes a page to fail W3C Validation and so they are not considered valid in this reference.
Description
The id attribute can be used on almost any element (see above) to specify a
unique identifier for that element. This id may then be referenced, for example,
within a script or CSS stylesheet or possibly by another
XHTML element which has an attribute of type
IDREF or
IDREFS.
id attributes:
- The identifier must follow the format specified for the ID Attribute Type (e.g. must not begin with a digit).
- Any single element may not have more than one
idand each such value must be unique to the document. - If compatibility is desired with HTML 4 identifiers, the ID value must match the regular expression
[a-zA-Z][a-zA-Z_:.-]*(see *HTML 4.01 - SGML basic types) - If compatibility is desired with CSS identifiers, the W3C's *CSS 2.1 - Characters and Case information should be noted.
See also the class attribute.
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Copyright © Sally Maughan 2005-2009 (Page last updated on 16 May 2009)
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Content based on the W3C Working Draft: *XHTML 1.1 and Recommendation: *XHTML Modularisation 1.1.
W3C, XHTML, XML, HTML, CSS and MathML are *Trademarks of the W3C (*MIT, *ERCIM, *Keio) with which the site's author has no connection.