the url is:
firefox is padding the bottom of the images (not the sides), and I can't seem to stop it.
so you know, the external stylesheet url referenced doesn't have any css - only what you see on this page.
It's because you're inlining
It's because you're inlining images, set img to display block and the gap on the content graphic closes, of course this makes a mess of the header links as you need them inline.
This really isn't the way to set up a layout, all decorative images should be set as backgrounds not foreground and your links should be a ul list with the graphics placed on the ul/li/a elements then you can use text along with sliced graphics that will expand with text re-sizing and all is nice and semantic.
Try looking for one of the guides such as sliding doors, although you don't need to take it to that level of complexity if the widths are fixed you can probably just place your graphics on the list element with matching background to fill in size increase.