One thing to keep in mind is that not all video cards function the same. a page at 800X600 on my laptop looks quite different than the same page at 800X600 on my desktop.
I'm using my laptop most at the moment for page work and it's resolution is 1280X800 (widescreen). I'd be willing to bet that someone with a different brand of computer set at 1280X800 would be seeing the page we are currently on at least slightly differently than I am seeing it now. There's too many variences, so that's why I would never take the attitude to design solely for the highest percentage from my stats.
I tweak my pages so they look OK at 1024X800 & 800X600 on both the laptop and PC, with medium-larger browser text sizes and anyone who insists on using outside those ranges can either scroll or squint
