p class="g1" span="3" >
    <col class="c1" />
    <col class="c2"/>
    <col class="c3"/>
  </colgroup>
  <colgroup class="g2" span="1" >
  </colgroup>
  <thead>
    <tr>
      <th>表头1</th>
      <th>表头2</th>
      <th>表头3</th>
      <th>表头4</th>
    </tr>
  </thead>
  <tfoot>
    <tr>
      <td>表底1</td>
      <td>表底2</td>
      <td>表底3</td>
      <td>表底4</td>
    </tr>
  </tfoot>