[SOLVED] Cross Browser Problem (posted in wrong section before)

Hi. I really have no reason to think this is Atahualpa related at all, but I will ask this and hope to get lucky. I built a site against IE8, not really knowing much at all about web standards markup compliance. It looks perfect in IE8..I have not tested it in other IE versions, but I have recently discovered that in Firefox, it is a pitiable mess. Here is a page link for any of you who don't mind having a peak in IE8 and Firefox so you can see the shocking difference. The home page is costructed differently, but it too appears butchered in FF.

Is there a relatively simple fix? I've tried X-Valid plugin, Total Validator online (which confuses me) and w3c validator. Am I on the right track?

I'm using Ata.3.4.6. and WP 3.0. Thanks!!