I would say that most designers design to fit an 800 x 600 resolution. Otherwise you can use percentages, which will conform to any screen size.
<div style='width: 98%;'>
Or perhaps a formula that will adjust pixel widths in the way that the aspect ratio is adjusted for images. Which could be accomplished with a bit of mathematics and likely javascript.
If you dabble much with absolute/relative positioning you'll find the percentage method has some drawbacks and that absolutely positioned elements don't always find their exact place when using percentage widths. And you will find that Gecko based browsers have some horrible bugs when using percentages on nested elements. (At least that's been my experience!)
My personal method, since my site relies heavily on positioning and layers, is a set pixel width designed to fit an 800 x 600 screen size, which is not uncommon.. I don't much notice it being too small.. I use a 1600 x 1200 resolution on a 22" monitor and 1280 x 1024 on a 17" monitor.. you might well go mad trying to find the right formula that jives with your aesthetic design! Because not only can the resolution vary, but different monitor sizes and settings might also factor in!
And here again, just my .02
: )
Rich
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Smiling Souls
http://www.smilingsouls.net
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