<ol>
  <li>first item</li>
  <li>second item  <!-- closing </li> tag not here! -->
    <ol>
      <li>second item first subitem</li>
      <li>second item second subitem</li>
      <li>second item third subitem</li>
    </ol>
  </li>            <!-- Here's the closing </li> tag -->
  <li>third item</li>
</ol>