<!doctype html>
<!--
     Any copyright is dedicated to the Public Domain.
     http://creativecommons.org/publicdomain/zero/1.0/
-->
<meta charset="utf-8">
<title>CSS Test Reference</title>
<link rel="author" title="Emilio Cobos Álvarez" href="mailto:ecoal95@gmail.com">
<style>
.container {
  background: gray;
  height: 80px;
}
.panel {
  background: lightblue;
  width: 150px;
  height: 80px;
}
.contents {
  height: 10px;
  width: 10px;
  background: purple;
}
</style>
</head>
<div class="container">
  <div class="panel">
    <div class="contents"></div>
  </div>
</div>