[Typo3] third level menu does not stay?

[Bing Du]

The site shows the following menu on the left.

level 1
    level 2

Here is the problem I'm experiencing.  Clicking 'level 2' shows:

level 1
   level2
      level 3

However, although clicking 'level 3' displays its page content fine, the 
menu changes back to:

  level 1
    level 2

Why 'level 3' doesn't stay?

Menu is constructed in typoscript as:

===========
temp.nav = HMENU
temp.nav.1 = TMENU

temp.nav.1 {
   expAll = 1
   wrap = <table width="150" border=0 cellspacing=0 
cellpadding=0><tr><td><img src="clear.gif" width=1 hspace=200 height=1 
vspace=3 border=0></td></tr> | </table>

   NO {
          linkWrap = {$menu.L0.fontWrap}
          doNotLinkIt = 1
          allWrap = <tr><td><img src="clear.gif" width=1 height=1 
vspace=3 border=1><br> | </td></tr>
   }

   ACT = 1
   ACT < .NO
}

temp.nav.2 = TMENU
temp.nav.2 {
   expAll = 1
   wrap = <tr><td nowrap><ul> | </ul></td></tr>

   NO {

     RO = 1
     after = <br>
     ATagBeforeWrap = 1
     linkWrap= {$menu.L1.fontWrap}
     beforeWrap = <li>
     stdWrap.field = title
     ATagParams = onclick="return toggleSubmenu(this);"
     allWrap = |
     after.field = uid
     afterWrap = <ul style="display:none;" id="page|">
     wrapItemAndSub = |<li></li></ul></li>
   }

   ACT = 1
   ACT < .NO
}

temp.nav.3 = TMENU
temp.nav.3 {
     expAll = 1
     NO {
     RO = 1
     after = <br>
     ATagBeforeWrap = 1
     linkWrap= {$menu.L1.fontWrap}
     beforeWrap = <li>
     stdWrap.field = title
     ATagParams = onclick="return toggleSubmenu(this);"
     allWrap = |
     after.field = uid
     afterWrap = <ul style="display:none;" id="page|">
     wrapItemAndSub = |<li></li></ul></li>
   }

   ACT = 1
   ACT < .NO
}
=========================

And here is the toggleSubmenu(this) function:

=====
function toggleSubmenu(link)
{
var temp = (link.href).split("=");
var div = document.getElementById("page" + temp[1]);

div.style.display = (div.style.display == 'block') ? "none" : "block";
if (div.innerHTML != '<li></li>') {
    if (link.className == "")
       link.className = "tempselected";
    else
       link.className = "";
    return false;
} else {
            return true;
        }
}
=====

I'd appreciate any help.

Bing