fijate si te sirve este codigo que arme:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Untitled Document</title>
<style>
body{
height: 100%;
margin: 0;
padding: 0;
}
.pricipal {
width:760px;
}
.header {
height:160px;
background-color:#999999;
}
.menu {
height:60px;
background-color:#666666;
}
.colLeft{
float:left;
width:260px;
background-color:#CCCC99;
height:auto;
}
.side1{
height:100px;
background-color:#CC33FF;
float:left;
width:260px;
}
.side2{
height:50px;
background-color:#FFCC33;
position: absolute;
bottom: 0;
float:left;
width:260px;
}
.colRight{
float:right;
width:500px;
background-color:#66CC33;
}
.content1 {
height:300px;
background-color:#00CCFF;
}
.content2 {
height:100px;
background-color:#00CC33;
position: absolute;
bottom: 0;
width:500px;
}
</style>
</head>
<body>
<div class="pricipal">
<div class="header">Header</div>
<div class="menu">Menu</div>
<div class="side1">side 1</div>
<div class="colRight">
<div class="content1">cont1</div>
<div class="content2">cont2</div>
</div>
<div class="side2">side2</div>
</div>
</body>
</html>