XML、php、js实现的树状导航的超链接如何设置?

源代码如下：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title></title>
</head>
<style>
a:hover {
font-size: 10pt; color: #FF6600;
vertical-align:middle;
}
a {
font-size: 10pt; text-decoration: none; color: #676767;
noline:expression(this.onfocus=this.blur);
text-align:left;
vertical-align:middle;
}
#HideDiv{
display:none;
}
</style>
<body>
<form id="form1" name="form1" method="post" action="" >
  <table width="372"  border="1" align="center"  bgcolor="#E6F2F2" bordercolor="#478D8D"  style="border-style:none" cellspacing="0" >
    <tr>
      <td   scope="col" align="center" style="border-bottom-style:none" >管理组织架构</td>
    </tr>
    <tr>
      <td >
       <table width="100%"  border="0" cellpadding="0" cellspacing="0" align="left">
        <?php
          //从XML文件中加载节点
          $xml_file = simplexml_load_file("org.xml");
     foreach($xml_file->children() as $node){
?>
          <tr>
           <td width="38%" align="right">
             <img src="images/rootnode.gif" width="15" height="15" border="0" >   </img>
           </td>
            <td  width ="62%"  left="0px" align="left" ><a href="#" onclick= "ShowNode(<?php echo $node ?>)">  
<?php echo $node ?></a>
            </td>
          </tr>
          <tr>
          <td width ="38%" align="center" >
          </td>
             <td  width ="62%" >
             <div id= <?php echo $node ?> style = "display:none" class="HideDiv" > 
                  <table width="100%" border="0" cellpadding="0" cellspacing="0" align="left" >
                 <?php
   foreach($node->children() as $value){
 ?>
             <tr>
                  <td width ="10%"  align="right" >
                          <img  src="images/childnode.gif" width="15" height="15" border="0" > </img>
                        </td>
                        <td  width ="90%"  align="left"  ><a href='#' >  <?php echo $value?></a>
                        </td>
               </tr>
                  <?php
}
          ?>
                   </table>
              </div>
             </td>
          </tr>
        <?php
 }
  ?>
        </table>
      </td>
    </tr>
  </table>
   
  <script language="javascript">
  function ShowNode(ParentID){
var Div = ParentID;
if (Div.style.display == "none"){
Div.style.display = "block";
}else if (Div.style.display == "block"){
Div.style.display = "none";
}
  }
  </script>
</form>
</body>
</html>
如何修改实现二级目录的超链接？