In reply to the bit about CSS validators inside browsers. Recent Mozilla versions have support for that in the javascript console.

Yeah, CSS validation seemed like something pretty obvious for the browsers to implement. They have to parse it, after all. Of course, if it was expressed in XM...no, nevermind. I'm glad to hear the exist, I'll have to give it a try. Thanks, Anne!

Somehow I think it would not make sense to express CSS in XML. After all, it was designed in the HTML browser era and has to be compatible with HTML. I guess CSS expressed as XML language might have its advantages but simple CSS selectors combined with declaration blocks are probably easier to understand for authors.

Besides that CSS does not know well-formed as XML does it. (It does have error parsing rules as opposed to HTML.) This makes it a lot easier for authors to create a style sheet.

Note the reference (http://norman.walsh.name/2004/12/15/examples/webarch.pdf) in your web recommendation essay (http://norman.walsh.name/2004/12/15/webarch) to the "nice pdf" doesn't work; presumably it should be to http://www.w3.org/2001/tag/2004/webarch-20041014/webarch.pdf ?

Yes, pointing to the W3C copy would be ok, but I'm pretty sure I meant to have the copy locally as well. It will be fixed momentarily. Thanks for letting me know.

Nightly trunk builds of the Mozilla Suite and Firefox have CSS parse error reporting in the JavaScript Console.