<html>
  <meta chartset=utf-8>
  <title>Test reference</title>
  <link rel="author" title="Florian Rivoal" href="https://florian.rivoal.net">
<style>
html {
  direction: rtl;
}
body {
  height: 0;
}
html::before {
  content: "This text must be on the right";
}
html::after {
  content: "This text must be on the left";
  display: block;
  direction: ltr;
}
</style>
<body></body>