Why are there people looking at the html code? Do you look at the binary in an mp3? ;-)
Nope, but i'm a bit of a css/xhtml/accessibility geek.
I frequently browse with stylesheets and images turned off (i'm on a shared dial-up connection at work and its dog slow) and you'd be amazed just how many sites break completely the moment I do this. Why?
No alt or title tags. Simple as that.
Every image should have an alt tag, even if its just a simple alt="" for spacer gifs (another hateful way of doing page layout but thats another story altogether ;-) )