If some CSS guru out there could assist, it would be greatly appreciated.

I have a website (http://www.clarksburgblueprint.com) which uses the following script:
http://www.clarksburgblueprint.com/css/clarksburg.css

When I adjust my resolution to 1152x864, the center content suddenly shifts down and makes the page twice as long. Any suggestions?

I'm new to CSS, but I'm sure that will be obvious! Thanks for your time.