Looks good!
For the background, I always use a png with transparency horizontally repeated, and a block colour background underneath for the rest of the page - e.g. In your case, a darker blue gradient to transparent, and then a lighter blue block colour background underneath. This should give the desired effect (Im not aware of browsers not supporting png's - if they don't they're far behind).
The best way to make content boxes with div's is pretty much however you want it to look; one, two, three+ columns... it's possible.
Good luck