<!DOCTYPE html>
<html>
<head>
<style type="text/css">
html {
margin: 0; padding: 40px 20px;
background-color: green;
}
body {
margin: 0; padding: 0 20px;
background-color: red;
div {
background-color: blue;
height: 20px;
</style>
</head>
<body>
<div></div>
</body>
</html>