quirks/html-fills-viewport-quirk.html

<!DOCTYPE quirks-mode>
<link
  rel="help"
  href="https://quirks.spec.whatwg.org/#the-html-element-fills-the-viewport-quirk"
/>
<link rel="match" href="html-fills-viewport-quirk-ref.html" />
<style>
  html {
    border: solid;
    margin: 10px 11px 12px 14px;
  }
  body {
    margin: 0;
  }
  span {
    display: inline-block;
    width: 100px;
    height: 100px;
    background: green;
  }
</style>
<body>
  <span></span>
</body>