Content - минимальная ширина, равна 510px для IE7(8beta2}, OPERA, FF, Chrome, SafariWin
<body>
<div class="header">Header</div>
<div class="middle">
<div class="content">Content</div>
<div class="left">Left</div>
</div>
</body>
* {margin:0;padding:0;}
html,body {background-color:#aaa;height:100%;}
.header {
background-color:#9c9;position:relative;z-index:2;
margin:0 auto;min-width:710px;max-width:900px;height:100px;
}
.middle {
margin:-100px auto;position:relative;
min-width:510px;max-width:700px;min-height:100%;
}
*html .middle {width:700px;height:100%;}
*html .header {width:900px;}
.middle,.content {background-color:#fff;border-left:#cc9 200px solid;}
.content,.left {border-top:#000 100px solid;left:-200px;overflow:hidden;}
.content {position:absolute;width:100%;}
.left {position:relative;width:200px;}