<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN">
<html lang="en">
<head>
<title>Margin Collapsing: negative margins (easy)</title>
<style type="text/css">
.container { background: red; height: auto; border: 1em lime solid; }
.a { margin-top: 1em; margin-bottom: 1em; }
.b { margin-top: 1em; margin-bottom: 1em; }
.c { margin-top: 1em; margin-bottom: 1em; }
.d { margin-top: 1em; margin-bottom: 1em; }
.e { margin-top: 1em; margin-bottom: -1em; }
.f { margin-top: 1em; margin-bottom: 1em; }
</style>
</head>
<body>
<p>There should be no red below.</p>
<div class="container">
<div class="a">
<div class="b"> </div>
<div class="c"> </div>
</div>
<div class="d">
<div class="e"> </div>
<div class="f"> </div>
</div>
</div>
</body>
</html>