<!doctype html>
<title>CSS Test Reference</title>
<meta charset="utf-8">
<link rel="author" title="Emilio Cobos Álvarez" href="mailto:emilio@crisal.io">
<style>
.parent {
  position: fixed;
  top: 0;
  left: 0;
  display: block;
  width: 200px;
  height: 200px;
  background: yellow;
}

.child {
  position: absolute;
  left: 50px;
  top: 50px;
  width: 100px;
  height: 100px;
  background: green;
}
</style>
<div class="parent"><div class="child"></div></div>
