<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title>:)</title>
<style>
#above, #below {
width: 300px;
height: 300px;
}
#above {
background-color: red;
position: relative;
top: 10px;
left: 15px;
}
#below {
background-color: green;
position: absolute;
z-index: -1;
top: 20px;
left: 20px;
/* весь этот говнокод ради ИЕ7 */
border: 0px solid green;
background-color: expression("transparent");
width: expression(this.oldWidth?1:(this.oldWidth=this.currentStyle.width),parseInt(this.oldWidth)-parseInt(this.currentStyle.left)+"px");
height: expression(this.oldHeight?1:(this.oldHeight=this.currentStyle.height),parseInt(this.oldHeight)-parseInt(this.currentStyle.top)+"px");
border-bottom-width: expression(this.currentStyle.top);
border-right-width: expression(this.currentStyle.left);
}
</style>
</head>
<body>
<div id="above">
Hello World
<div id="below"></div>
</div>
</body>
</html>