怎么样去除不匹配的标签,在XML(html)没有前标[eg:<D>],但出现了后标[eg:</D>]
<div align='center' id='year_copper_lme_mt'>
  <table>
  <tr>
  <th colspan='6' class='tbltitle'>
  copper lme cash and 3 month official seller / settlement prices 2010 <small>usd/mt</small>
  </th>
  </tr>
  <tr>
  <td>
  avg 7,386.25 <span>7,412.03</span>
  </td>
  <td>
  avg 6,848.18 <span>6,872.45</span>
  </td>
  <td>
  avg 7,462.83 <span>7,494.85</span>
  </td>
  <td>
  avg 7,745.08 <span>7,780.68</span>
  </td>
  <td>
  avg 6,837.68 <span>6,874.08</span>
  </td>
  <td>
  avg 6,499.30 <span>6,530.00</span>
  </td>
  </td></tr>
  <tr>
  <td>
  </td>
  </tr>
  <tr>
  <th class='tblhead' align='center'>
  jul
  </th>
  <th class='tblhead' align='center'>
  aug
  </th>
  <th class='tblhead' align='center'>
  sep
  </th>
  <th class='tblhead' align='center'>
  oct
  </th>
  <th class='tblhead' align='center'>
  nov
  </th>
  <th class='tblhead' align='center'>
  dec
  </th>
  </tr>
  <tr>
  <td>
  <table>
  <tr>
  <td>
  </td>
  <td >
  cash
  </td>
  <td>
  3 mo
  </td>
  </tr>
  <tr>
  <td>
  <span>1</span>
  </td>
  <td>
  6,354.00
  </td>
  <td>
  6,389.00
  </td>
  </tr>
  </table>
  </td>
  <td>
  </td>
  <td>
  </td>
  <td>
  </td>
  <td>
  </td>
  <td>
  </td>
  </tr>
  </table>
  </table>
</div>
红色的为多余的两个后标,现在想在C#程序中通XMLDocument