title: this.nextSibling not working
body: <p>I expect the following code to alert "out"</p>
  
  <pre><code>&lt;input type=text onfocus="alert(this.nextSibling.id)" /&gt;
  &lt;output id="out"&gt;this is output&lt;/output&gt;
  </code></pre>
  
  <p>But it alerts undefined
  WHY?</p>