<!DOCTYPE html>
<html>
<head>
<style type="text/css">
#separator-top {
 height: 20px;
 margin-bottom: 20px;
 background-color: green;
}
#overflow {
 background-color: green;
 height: 40px;
}
#separator-bottom {
 height: 20px;
 margin-top: 20px;
 background-color: green;
}
</style>
</head>
<body>
<div id="separator-top"></div>
<div id="overflow"></div>
<div id="separator-bottom"></div>
</body>
</html>