Shouldn't the question be: how big is your browser window?
I run at 1600x1200 (desktop) and 1024x768 (laptop), but my browser window is only about 700 pixels wide. The web isn't everything, I wanna be able to see other windows too.
You should be designing the pages to adapt to whatever (within reason) the size of the user's browser window, this isn't hard to do.
-Tim
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