message: Moved iframe loading to bottom of body.
diff: <meta charset="utf-8">
  <meta http-equiv="x-ua-compatible" content="ie=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  - <iframe style="display: none" id="sandbox" src="sandbox.html"></iframe>
  <title>Selenium IDE</title>
  </head>
  <body>
  <div id="root"></div>
  <!-- script -->
  + <iframe style="display: none" id="sandbox" src="sandbox.html"></iframe>
  </body>
  </html>
  