the current W3C reccommendations are device resolution independent, Ems %age dimensions adjust to all screen sizes and user preferences
Web editors that can layout in % are freely available
Web editors that cant, can be converted
example if you design for 800*600
width=80px becomes width=10%

thanks almostbob, and kipl20 remember when u're starting to design your website at 1024x768 resolution, there's always a space for the scrollbar on your browser, thus u have to contract the width to 1000 px.

Usually, you can make it up to 1024 by 768. It's nice to have the important stuff above the 'fold', though. That's where you have to scroll further, and estimating it at about 700-800 would be a good idea.

Of course, there are some nice sites which use fixed-width layouts. You can put everything in a 'wrapper' div and then use margin:auto to center it. That works well if it's not so much text, but images and snippets of text/widgets/blank space and the like.