Instead of using px for widths use % that way the site will always be a % of the screen size.
<div id=container>
<div id=header>...</>
<div id = mainbody>...</>
<div id = footer>...</>
</div>
css
#container { margin: 0 auto; max-width: 100%; width: 60em; }
#header { border-bottom: 0.5em solid; clear: both; float: left; line-height: 1; width: 100%; }
#main { width: 66.67%; }
#footer { width:100% }
hope that helps
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If the human brain were so simple that we could understand it, we would be so simple that we couldn't. - Emerson M. Pugh