I took a peek at your code and you're missing the opening <html> and <body> tags (though you close them at the end). IE forgives, lesser gods do not.
If it's important to the look of your page to maintain a white background make sure that you specify bgcolor="#ffffff" in the body tag. I set my default window background color to a middle gray to reduce eye strain when I'm coding and some browsers will carry this setting over as a default background for the browser window. Looks fine on Yahoo where they have always intended the bgcolor to be customizable, but looks slightly less good on sites that haven't allowed for it intentionally.
I noticed that you're embedding your CSS in the header of each page. While you're probably plopping this in from a template with PHP, you should still consider moving it out to a separate file and just targeting it with a link tag: <link rel="stylesheet" href="/styles.css" type="text/css">. This will make your pages more accessible to users who, for some reason (physical or equipment disability), need to define their own stylesheet controls and override yours.
Hope this helps, and good luck with the site.