<!DOCTYPE HTML>
<html>
<head>
<style>
#asd{
width:300px;
height:200px;
background-color:blue;
position:absolute;
left:0px;
right:0px;
top:0px;
bottom:100px;
/*margin:auto;*/
margin-top:auto;
margin-bottom:auto;
margin-left:auto;
margin-right:auto;
}
</style>
</head>
<body>
<div id="container">
<div id="asd">
</div>
</div>
</body>
</html>