<!doctype html>
<html>
<head>
<style>
.outer {
position:relative;
left:0px;
top:0px;
width:
200px;
height:100px;
border:none;
background:#00ff00;
}
.inner {
position:absolute;
left:0px;
top:0px;
width:50px;
height:50px;
background:#ff0000;
}
</style>
</head>
<body>
<div class=outer><div class=inner></div></div>
</body>
</html>