When people talk about microformats, they often have the same bit of confusion about the class attribute; it is often referred to as a “css class.”

I’m not criticizing anyone here, I just want to point out that there’s some confusing regarding the class attribute.

In the HTML 4 spec (from which XHTML is derived), classes are defined to have these purposes:

The class attribute, on the other hand, 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 has several roles in HTML:

• As a style sheet selector (when an author wishes to assign style information to a set of elements).
• For general purpose processing by user agents.

There’s a couple of points I’d like to highlight here:

First, notice that classes are multivalued, meaning that elements can have one or more, space-sepearted values.

Next, notice that class values are not just for styling. While this is certainly the most common and well-known use for class values, they are open “for general purpose processing by user agents,” which could easily include non-intrusive scipting and semantics. In fact, classes actually work best when treated as a mechanism for applying semantics, rather than just hooks for styling (see Tantek’s Class for Meaning, not for show).

For a more thorough primer on the use of class values, and how they relate to document structure, see Tantek‘s post, A Touch of Class, which though its 3 years old, is just as relevant today.

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