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About your situation, though... you'll need to provide more details! Imagine if you were in my position... what do I know about your site or the way you coded it? absolutely nothing.
The problem really seems to be that the images and tables it uses for it's layout are an absolute size, and sized for an 800x600 screen... you'll need to change widths of certain tables (and possibly images) to display in larger dimentions, or even in variable dimentions, with max and min widths (note: max and min settings don't work on IE unless you do one of many fixes for it though)
Note: don't link your webpage, you are only allowed to post it's code.