<!doctype html>
<meta charset="utf-8">
<title>CSS test reference</title>
<style>
  body { margin: 0 }
  :root {
    box-sizing: border-box;
    width: 100%;
    height: 100%;
    border: 1px solid black;
  }
</style>
<div>I should not overflow to the next page.</div>
