<!DOCTYPE html>
<body>
  <iframe></iframe>
  <script>
    var win = window.frames[0];
    win.document.open();
    win.document.write("<!DOCTYPE html><html><head></head><body></body></html>");
    win.document.close();
    win.document.body.innerHTML = "<link rel='stylesheet' type='text/css' href='outer-sheet.css' />";
    win.document.body.innerHTML += "<p style='padding:2px'>test</p>";
  </script>
</body>