'@Jakob - I'd agree screen resolution isn't a great...'
From the comments on 'Screen Resolutions and Aspect Ratios Worldwide'
@Jakob - I'd agree screen resolution isn't a great measure for design - my native screen res is 2560x1600, and I wouldn't dream of running a maximised window. At the lower end - 800x600, 1024x768 etc, it's probably more of a consideration.
Whilst there's no concrete link between actual browser size and screen size, it's likely there'll be some correlation. I just wish we could all produce 100% fluid, 100% scalable designs :-)