You might consider slicing up the background image - four or five smaller images load faster than one huge one. I'm sharing a 25k dial-up connection with two other computers (no lie), and my fiancé doesn't like when I use up our speed by loading graphics. :P
Anyway, I can tell that you probably don't see the white space (800x600, right?), but in a higher resolution the grey stops and there's a giant white space around it. That's because your background code isn't working properly. Most browsers will only read one body tag and you've got four. Consider cleaning this up a bit and implementing everything into your CSS:
It may be different than what I'm seeing in your source code, but you've got a lot of code in the body that belongs in the head, such as style tags and the title.
But yeah, it really does look good, I'm just helping work out the bugs and such. :)