<!DOCTYPE html>
<html>
<head>
<style type="text/css">
html, body {
 margin: 0; padding: 5px;
}
#positive, #negative {
 height: 20px;
 background-color: blue;
}
#margin {
 height: 10px;
}
#negative {
 background-color: green;
}
</style>
</head>
<body>
<div id="positive"></div>
<div id="margin"></div>
<div id="negative"></div>
</body>
</html>