You are missing a whole chunk of information that needs to be in your
The best solution is to open the
header.php in your theme and in the Default WordPress Theme and compare the two. Copy over the top information from the Default Theme into your Theme header and then try this again.
I bet that will fix it.
Specifically you are missing:
<meta http-equiv="Content-Type" content="<?php bloginfo('html_type'); ?>; charset=<?php bloginfo('charset'); ?>" />
But compare the two and add the missing elements.
Oh, and why not move the big lump of CSS to the style sheet so everything is in one place. Keeps things nice and clean that way, though some people don't do it. The site is simple enough to have it all in the style sheet.