<!DOCTYPE html>
<html>
<head>
<style type="text/css">
#float {
 float: left;
 width: 100px; height: 100px;
 background-color: blue;
}
#static {
 margin-bottom: 40px;
 height: 20px;
 background-color: green;
}
#clear {
 margin-top: 40px;
 clear: both;
 height: 20px;
 background-color: green;
}
</style>
</head>
<body>
<div id="float"></div>
<div id="static"></div>
<div id="clear"></div>
</body>
</html>