html中的div怎么用？

Question

<div id='aaa'>
  <table width="75%" border="0">
    <tr>
      <td>Get the filename associated with this part, if possible. Useful if this part represents an "attachment" that was loaded from a file. The filename will usually be a simple name, not including directory components.
Returns:
Filename to associate with this part</td>
    </tr>
    <tr>
      <td width="18%">朋友姓名:<img src="images/img_root1.gif"></td>
    </tr>
    <tr>
      <td>留言:<img src="images/img_root2.gif"></td>
    </tr>
  </table>
</div>
function dd()
{
alert(document.all.aaa.innerHTML);
}
</script>
<a href="javaScript:dd()">aa</a>