What’s a good screen resolution to design for?

Matt's answer:
CUTTS: Michael Quinn in Australia asked what screen size do you consider to be the default size for “above the fold” content on a website? Obviously, different screen sizes and resolutions will show more or less. So what’s the good standard to work with? Well, you’re sort of asking a Web design question, and I wouldn’t claim to be a Web designer, but I threw in my Google Analytics stats and looked at the most recent 300,000 visits. And out of the top nine different things as far as most popular screen resolutions, all of them were bigger than 800 x 600. The smallest vertical resolution was 768, and so there are some of those Netbook form factors. But I think if you are talking about above the folds of vertical, it, you know, a vast majority like 75, even 80% of the track that I get, all of those screen resolutions are 768 or more on the vertical side. So, that seems like a pretty safe thing to do. A lot of people feel like you have to code for 800 x 600 or even 1024 x 768. And that might be okay, but the Web is getting better and screen sizes are getting larger. So unless you have something that’s specifically dedicated to Web T.V. or to browsing the Web on a Wii, you can probably count on relatively reasonable screen sizes at this point.
by Matt Cutts - Google's Head of Search Quality Team