I’m running1400x1050 on my 20″, but I think that you are way off on your estimate on the number of people running at 800×600. I work on a lot of various people’s computers and almost never encounter a resolution that low. After all, that is the lowest resolution that XP easily lets you set. Big monitors are cheap, now and 800×600 looks really clunky on anything larger than a 14″ monitor.
All of this moot, anyway. A good webmaster will take into account that not all will be using the same resolution and design his site to accommodate a wide variety of resolutions and browsers. It is a cop out to design for one resolution and one browser and then proudly announce “Best viewed at 800×600 in Internet Explorer 6.”
The solution is easy, though. Do not use fixed pixel sized tables and columns. Looking at the CSS file it specifies the font size of the messages as “x-small”. This does not work out in too many cases. This designation is usually used for disclaimers and copyright info at the bottom of a page, not the content. It is better to set font size by points or even pixels. After all, the default font size for most word processors is 12 pt. 10 pt is not an unreasonable request for the content.