With the adoption of bigger displays with higher resolutions the screen resolution as an important variable in web design are getting obsolete.
The correct variable would be browser window size, because not all the users are browsing the Web with fully expanded browser window, but the problem is that no analytics tool (that I know of) measures this variable.
I want to create a statistic that gathers data and from visitors and shows the difference between browser window size and screen resolution.
If you want to participate in this statistic please visit the data gathering site here: http://playground.primalskill.com/browser-window-size/
Once I gather enough data I will show the results on my blog, but also here on this forum for Sitepoint users.