gecko-dev/layout/reftests/margin-collapsing/block-no-content-3a.html

<!DOCTYPE html>
<html>
<head>
<style type="text/css">
#separator {
 height: 20px;
 background-color: green;
}
#parent {
 background-color: green;
 margin-top: 10px;
}
#first-child {
 margin-top: 20px;
 margin-bottom: 30px;
}
#last-child {
 height: 20px;
 margin-top: 15px;
}
</style>
</head>
<body>
<div id="separator"></div>
<div id="parent">
 <div id="first-child"></div>
 <div id="last-child"></div>
</div>
</body>
</html>