12. XHTML Core Attributes Module


This section is normative.

This module defines the Core attribute collection.

12.1. Core Attribute Collection

class = NMTOKENS
This attribute assigns one or more class names to an element; the element may be said to belong to these classes. A class name may be shared by several element instances.

The class attribute can be used for different purposes in XHTML, for instance as a style sheet selector (when an author wishes to assign style information to a set of elements), and for general purpose processing by user agents.

For instance in the following example, the p element is used in conjunction with the class attribute to identify a particular type of paragraph.

<p class="note">
These programs are only available if you have purchased
the advanced professional suite.

Style sheet rules can then be used to render the paragraph appropriately, for instance by putting a border around it, giving it a different background colour, or where necessary by not displaying it at all.

id = ID
The id attribute assigns an identifier to an element. The id of an element must be unique within a document.

The id attribute has several roles in XHTML:

As an example, the following headings are distinguished by their id values:

<h id="introduction">Introduction</h>
<h id="events">The Events Module</h>
title = Text
This attribute offers advisory information about the element for which it is set.

Values of the title attribute may be used by user agents in a variety of ways. For instance, visual browsers should display the title as a "tool tip" (a short message that appears when the pointing device pauses over an object). Audio user agents may speak the title information in a similar context.

Example of the use of title:

<a href="Jakob.html" title="Author biography">Jakob Nielsen</a>'s Alertbox for January 11, 1998

Implementation: RELAX NG