Wc3 validator and cleaning things up - starting to get buggy 'round here

Why is it that whenever I ''think'' everything is running ok enough to get back in to working on content that everything falls to shit? In short, my site is badly misbehaving and some incredibly helpful wpmu users have been holding my hand (thanks jonathan and gina) through some possible fixes. Probably a fresh install is just what I need.....But, until then - here is where I am at:

I ran the WC3 validator and my landing page/home page is returning 52 errors and 48 warnings. I was wondering if any of you have knowledge of WC3? It's a brilliant validator engine - unfortunately, I am not brilliant and can't figure out how to fix the errors. For example: I enter my url at http://validator.w3.org/, it returns all errors and warnings for that url, line by line. Where I am lost is where specifically those lines are in my database? Like where exactly is line 75, column 16 located so that I can go in and fix it?

I am sorry if this is such a simple thing....i'm just not getting it. I have upgraded firefox and it is not compatible with firebug