+1 for strict. +2 for xhtml. Transitional is for the soft!

Might as well close all them tags. When it comes time to seriously mess with the dom or include microformats or you need to do some screen scraping, well formed XML is your friend. Seriously, don't fear the strict - it's really not much more. In fact, I don't even know what the difference is anymore. Personally, I don't really care if most sites I build validate but I can't help it - I love that green bar.
For the OPs width problem, I'm willing to bet it as something to do with the fact that you have it set @ 100% _and_ have either left/right margin, padding or borders. 100% plus 2px of border = more than 100%.
