Percentage widths for a whole webpage worked reasonably well a few years ago but more and more people are using large resolution monitors so a flexible page now needs to look good for old computers using 500px wide or 800*600 screen resolutions right up to 1920*1200, so the answer is to test your design at these resolutions. It will be difficult to get it looking good at all resolutions.
You can use min-width and max-width and perhaps set min-width at 780px width and max-width at say 1180px (allowing 20 px for a vertical scrollbar in 800 and 1200px wide resolutions).
http://www.wickham43.supanet.com/tut...xminwidth.html
However, min-width and max-width don't work in IE6 so you will need to fix the width in a conditional comment just for browsers IE6 or less. If you don't state a width for IE6 it just uses either the max-width or min-width as a fixed width, I can't remember which it uses.
http://www.wickham43.supanet.com/tut...tionalcomments
Put the conditional comment in the head section after the main stylesheet link with the min-width and max-width.
Code downloaded to my PC will be deleted in due course.
WIN7; IE9, Firefox, Opera, Chrome and Safari for Windows; screen resolution usually 1366*768.
Also IE6 on W98 with 800*600 and IE8 on Vista 1440*900.