I used the latest version of the "andreas01" design by Andreas Viklund to design Bejtlich.net. I used an older version of this CSS design for TaoSecurity.com, so I will probably upgrade when I have time.
I have to say I had no real trouble using CSS, unlike Mr. Dvorak. Needless to say my two sites are much simpler than his, and I would dare say far less gaudy!
Thanks to Royce for mentioning the HTML Validator Extension -- I plan to use it to fix warnings and any errors.