Refresh . My example is modified according to the updated question.
Here is a working example of your layout. Tested in IE8, IE7, Firefox and Chrome.
middle 100%. , top bottom header btm ( 120px).
middle 100%, , big, 100% body, , , middle , .
<!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>
<title></title>
<style type="text/css">
html
{
height: 100%;
}
body
{
background-color: #EEEEEE;
height: 100%;
padding: 0;
margin: 0;
}
#big
{
width: 100%;
height: 100%;
}
#header
{
width: 100%;
background-color: #DDD;
height: 120px;
}
#btm
{
width: 100%;
height: 120px;
position: absolute;
bottom: 0px;
background-color: #999;
}
#middle
{
width: 100%;
position: absolute;
top: 120px;
bottom: 120px;
}
</style>
</head>
<body>
<div id="big">
<div id="header">
header
</div>
<div id="middle">
middle
</div>
<div id="btm">
bottom
</div>
</div>
</body>
</html>