I've been using this cool little tool lately to narrow in on some code problems: http://validator.w3.org/ It's a nice way to find exactly where your errors are, (if any) and what you should do to fix them. I found it interesting to check up on a few big names: microsoft.com currently has 2 errors msn.com passed with 0 errors apple.com currently has 9 errors google.com currently has 55 errors... mozilla.com passed with 0 errors myspace.com currently has 133 errors! Microsoft and Mozilla win. Of course ITforum.com currently has 45 errors.. (Booo!) but they are mostly stupid things like embedded tables.. hehe. I just started fixing this today though and I've knocked down quite a few errors so far. Shooting for passing with 0 errors soon.
Along with this, I recommend the O'Reilly book Head First HTML with CSS and XHTML... it's the textbook for my Internet Programming class, and I have to say it's the best textbook I've ever bought. They cover these standards really well.
