<!DOCTYPE html>
<meta charset="UTF-8">
<title>CSS Reference</title>
<link rel="author" title="Xidorn Quan" href="https://www.upsuper.org">
<link rel="stylesheet" href="/fonts/ahem.css">
<style>
  .rel { position: relative; }
  .abs { position: absolute; left: 0; top: -1em; }
</style>
<body style="font: 50px/3 Ahem">
X<span class="rel"><span class="abs">X</span></span>