I'm glad to see so many people care about using valid code.

I was bummed to find out how many popular sites aren't:

msn.com - 22 errors
google.com - 47 errors
ebay.com - 199 errors and they didn't even bother setting a doctype.

A lot of the problems are pretty small and for now I don't think its that important. Sooner or later its going to become a problem though.