Let me warn you in advance, though: if you intend to present a different Website for each common screen resolution, you're making a lot of work for yourself. Consider a different page layout that is less resolution-dependant. Large, screen-filling background images are an especially bad idea.
Yeah... Better invest your time in making a site which fits in every resolution cause have to set up 4 different sites and than later add content to all 4 of them takes a lot of time. And time is money