Ugh, no. This penalizes people with larger screens. 1920x1200 = two windows of 960px 2560x1600 = three windows of ~850px
the other problem with this and fluid designs on wide screens is that it becomes difficult to read text when it is that wide.
the best idea that i have seen is a site (or maybe it was sites, i know I've seen at least one), where the content is 960px but then if your browser window is wider, javascript adds additional content to the right of the content, columns that come down with additional links and further navigation options.