Building a web site? One important question, if you’re developing (as most do) to a fixed pixel size, is how big your users’ screens are. Not just the average user, either; you should keep at least 95% of your potential audience happy. Even 1% of visitors annoyed is a risk: are they the ones deciding if they’re going to buy or recommend your product? If you exclude Mac users, for example, you’re missing out on a vocal population of important bloggers and pundits.
It’s happened to me. In the late 90s I designed a multimedia project called Xstream to use an 800×600 screen, using Director. Of course, the one guy with a 640×480 screen was the guy who had to approve the thing.
So, how big are their screens? Well, it’s not even that simple. On Windows, most users browse at full screen. On Mac, few do; the multi-window philosophy has been around too long. As screens get larger and full-screen browsing becomes less practical, browser sizes will become less predictable.
The bottom line? If you want to please 95% of the global audience, your core content should fit within 787×423 pixels without scrolling. Not scary enough? Only about 50% of the audience can see more than 600 pixels vertically or around 1024 pixels horizontally at once.
Lastly, bear in mind the iPhone’s variable sizing and lack of Flash support. It’s going to be big and you don’t want to be left out.