<!DOCTYPE html>
<meta charset="utf-8">
<title>Reference for negative margins</title>
<link rel="author" title="Google Inc." href="https://www.google.com/">
<style>
.container {
width: 40px;
height: 10px;
background-color: green;
border: 3px black solid;
}
</style>
<body>
<p>You should see a green rectangle with a black border, 40px wide. You should see no red.</p>
<div class="container">
</div>
</body>