User blog comment:Sarah Manley/New themes for the Monaco Skin/@comment-1025281-20100331081922

A fixed width helps because admins customising the look and feel of a site can be sure what they are looking at is close to what everyone else is looking at. This is especially true of main pages; it can be frustrating to format everything exactly using a 1280 width screen, and then discovering that everything breaks at 1024.