If you have really wide <pre> stuff in the body section, the banner can get drawn too wide by most browsers. In this case, you might want to put the wide body text in a continuation section.
Text in the sidebar can wrap, which sometimes makes it look ugly. The alternative is to prevent wrapping by inserted non-breaking spaces (i.e. ) instead of soft spaces.
The mixin class structure doesn't work as well as I'd like. Writing the style class is more awkward than it should be, but at least there are enough examples for you to go by.