Oh you know what? I bet your browser is just caching the old CSS file. Try just clicking "Reload" and if that doesn't do it, clear your cache. But I checked your site with Firefox, IE6 and IE7 and it looks right to me on all.
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The day Microsoft makes a product that doesn't suck is the day they make a vacuum cleaner.
I had the same problem, both here at work (IE) and at home (Opera/Mozilla). Both places the problem seemed to clear itself up, so I probably had a reload at some point.