Not everyone has the same screen, so it would make a difference to a web site. If the site is coded at a huge resolution, like my laptop's 16 inch screen for instance, anyone with a smaller screen would be scrolling all over the place to view your entire site. A few web design programs do ensure that your site is seen properly without having to scroll, but what I found useful is centering the page slightly on the background so that no one would have to scroll and the only major difference you would notice is the size of your background.

Hope it helps
Phoenyx