I know it is belated, but here is my two cents anywho.
Using CSS, with a 28px x 1200px (width x height) image for my background, I was able to click the edge of the screen and drag the screen all the way, centering all my contents. My horizontal navbar also used a repeating background to auto-size to the resolution of a given users screen, and it also expanded the entire width of the two monitors. I must say though, if the page is small, the results are quit humerous.
I also have two monitors, with different resolutions and both screens were filled totally. Showing people this always manifests, oooh's and aaaah's. As far as a script or server side include im sure there is one out there somewhere, but it can be accomplished with CSS and XHTML.