Impressive CSS
Take a look at this page in Mozilla, view the source code and ask yourself “how on earth did he do that?”. It appears to involve very creative use of borders, possibly relating to the fact that a single border in CSS (at least in Mozilla and presumably in IE5/Mac as well) is actually a trapezium, not a line. Tantek Çelik was the project lead for IE 5 for the Mac (and the creator of both the Box Model hack and the High Pass Filter) so general CSS wizardry is to be expected.