I've been a huge fan of sites running "Some Type" of validity, may it be XHTML/CSS, HTML4.x or even some of the various accessability requirements out there...
Over the last month (since I got laid off) I've had to find something to do, so I figured I'd finally get around to doing something on
UGN Security which I did... I went ahead and not only PHPified my site, I also made sure it was both XHTML and CSS valid; though I hadn't had a chance to run it through any accessability engines (yet anyway)...
It suprisingly wasn't as hard as I had planned, but once i got started it was pretty hard to stop (unlike the last couple of times I had stared)...