You can, of course, use any convention you like. But too many times I've seen style namespaces which tend to follow the values of the first style sheet, instead of concentrating on the actual content ..erm.. context.

What I mean is, if you have a header box on a page that, in your first iteration, happens to be big and red, for heaven's sake don't go naming the element style "bigandredbox"--that defeats the purpose of separating content and style. Name it "mainheader" or something. That way, when They decide it should be blue, you don't have a conundrum of naming illogic. It's a maintainability thing.