Designing for actual browser sizes
Update December 2008: Thomas has published a follow-up article, “Browser sizes revisited.” The practical advice is: Design websites to be no wider than 980px. The reasons: Even though most people are browsing on 1280x800 monitors these days, they keep their browser windows minimized to a width between about 1200 and 1300 pixels. The other reason is that mobile phone web browsers all use 980 as their default width.
Original entry: Thomas Baekdal has published a report that fairly definitively puts to rest the notion that there are a lot of people still using 800x600 as their monitor size and therefore that websites should be narrower than 800 pixels.
I've been saying for more than three years that the data show that 1024x768 has been the norm both worldwide and in North America, and the number of people using that resolution has not surprisingly increased a great deal in those three years. Actually, there are a lot of people using much larger monitor resolutions these days.
The report is will researched, and the user types and geographical breakdown is broad, although I wish there was a slightly larger number of actual domains that were used for testing. But at least the type of sites used — primarily fashion sites for teens, men, and women — would presumably cover a fairly accurate and broad age range.