[balinor]

This is one of those topics that is highly debatable, but always plan for the worst case scenario.

100% width is always safe, but can create some ugly layouts on laptops and for people who use high resolutions. Drives graphic designers nuts :)

800x600 is still around, but it is becoming less so as most of the major computer manufacturers are shipping computers set at 1024x768 now. You have to assume that quite a few people out there have no idea how to change that setting. Also, keep in mind that when a computer is set at 800 pixels wide, the browser doesn't actually stretch that far. Some people have toolbars or the media browser on the side, which can take some room. So, to be completely safe, use something like 750 pixels wide, centered.

If you want to go by the percentages, 1024x768 is pretty much the standard these days, so set the width to 975 or so to allow for some 'stuff' on the sides.