<!DOCTYPE html>
<html>
<head>
<style type="text/css">
#a {
 height: 4em;
 background-color: green;
 overflow: hidden;
}
#a div{
 position: absolute;
 top: 1em; left: 1em;
 background-color: lime;
 height: 7em; width: 7em;
}
</style>
</head>
<body>
<div id="a">
 <div></div>
</div>
<textarea>    FAIL</textarea>
</body>
</html>