<!doctype html>
<title>CSS Test Reference</title>
<link rel="author" href="mailto:emilio@crisal.io" title="Emilio Cobos Álvarez">
<style>
html, body { margin: 0; padding: 0; }

.content {
  margin-top: 100px;
  width: 200px;
  height: 200px;
  background: blue;
}
</style>
<body>
  <div class="content"></div>
</body>