Web Design in a Nutshell, 3rd Edition

class identifier

The class attribute is used for grouping similar elements. Multiple elements may be assigned the same class name, and doing so enables them to be treated similarly.

In the span example above, the telephone number was identified as telephone with the class attribute. This implies that there may be many more telephone numbers in the document. A single style sheet rule could then be used to make them all bold and blue. Changing them all to green requires editing just one line of code. This offers an obvious advantage over changing color one by one with the deprecated font element. In addition to being inefficient to maintain, font doesn’t add any semantic cues for user agents.

According to the HTML 4.01 specification, the class attribute may be used:

• As a style sheet selector

• For general purpose processing by user agents

In HTML 4.01, id and class attributes may be used with all elements except base, basefont, head, html, meta, param, script, style, and title. In XHTML, id support has been added to those elements.