page.html

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <title>Elements in the frame</title>
    <meta property="og:title" content="Elements in the frame" />
    <meta property="og:type" content="website" />
    <meta name="twitter:card" content="summary" />
  </head>
  <body>
    <main>
<p>Page content.</p>
</main>
    <site-footer><footer>Elements in the frame</footer></site-footer>
  </body>
</html>