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In what way doesn't it work?
I've done themes that are fixed width, and others that stretch to fit screen resolution, either way is not that difficult.
I've also done a theme that has 2 versions depending on screen resolution - it uses javascript to sense the user's resolution, then directs to the appropriate style sheet. I have one for 800 x 600 and under, another for over 800 x 600. These are both fixed width. There's nothing to stop you from specifying more sizes.