Did you know that about 30% of internet users have their monitors set at a resolution of 800 x 600 px, the majority now have their monitors set at 1024 x 768 px.
But what happens if your web site is designed at a width suitable for the majority? 30% of your visitors will have to scroll horizontally to fully view your site.ARGHH!! Horrizontal scrolling is not an intuative action of any surfer and there is no telling what important information or message they may be missing.
Until the 800 x 600 viewer statistics drastically drop we will always be designing so our web sites with optimal usability for the lowest common denominator.