It really depends...I personally don't ever design with a width of more than 750px...if you want to be a purist, don't go over 640 x 480...even though many people will say this is no longer true, when I look at my webstats, each month there is always a few people with that resolution and I wonder if they missed any info by not scrolling left or If I lost them due to the fact that they have to scroll left to view my sites. If you want to get tricky, do a google search for CSS Liquid Layouts... then you can make this question disappear altogether. if you stick with 760 x 420 you should be safe if you want the page to fit without any scrolling whatsoever, but even then you run the chance that their browser is not maximized. I usually run at a resoution of 1280 x 1024, but I will usually set a custom size for my browser so that it does not take up the whole screen and I can click on other apps, that I have running behind the browser, so there is really no way of making your page fit on everyones screen unless the width of your site is set dynamically.