The CLASS Attribute
The CLASS attribute is used to specify the style class to which the element belongs. For example, the style sheet may have created the punk and warning classes:
.punk { color: lime; background: #ff80c0 } P.warning { font-weight: bolder; color: red; background: white }These classes could be referenced in HTML with the CLASS attribute:
<H1 CLASS=punk>Proprietary Extensions</H1>
<P CLASS=warning>Many proprietary extensions can have negative side-effects, both on supporting and non-supporting browsers...In this example, the punk class may be applied to any BODY element since it does not have an HTML element associated with it in the style sheet. Using the example's style sheet, the warning class may only be applied to the P element.
A good practice is to name classes according to their function rather than their appearance. The warning class in the previous example could have been named red, but this name would become meaningless if the author decided to change the style of the class to a different color, or if the author wished to define an aural style for those using speech synthesizers.
Classes can be a very effective method of applying different styles to structurally identical sections of an HTML document. For example, this page uses classes to give a different style to CSS code and HTML code.