I think, just to make it more professional, that IPB should make a valid HTML :wacko:.
Even with one of the most basic tags (img) there is not alternate text.

It would be great if 3.0 had 100% valid html ^_^
Not to be one to compare, but phpBB3 has valid html and IPB which is far better doesn't :o

IPB 3 will have valid XHTML.

http://forums.invisionpower.com/index.php?showtopic=273408