Expanding type menu

Ok, im building a menu, and i want to so that if i click a button parts of the menu appear or disapear and when i click the same button it either disapears or appears dependin on the state it is in. i have this code below but cant make it so that it can appear after disapearing on the same button, please help

Code:

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<!-- menu -->
<script type="text/javascript">
<!--
  HM_DOM = document.getElementById ? true : false;
  HM_IE  = document.all ? true : false;
  HM_NS4 = document.layers ? true : false;
  function HM_f_ToggleElementList(show,elList,toggleBy) {

      if(!(HM_DOM||HM_IE||HM_NS4)) return true;

      if(HM_NS4&&(toggleBy=="tag")) return true;

      for(var i=0; i<elList.length; i++) {
        var ElementsToToggle = [];
        switch(toggleBy) {
            case "tag":
              ElementsToToggle =
    (HM_DOM) ? document.getElementsByTagName(elList[i]) :
    document.all.tags(elList[i]);
              break;
            case "id":
              ElementsToToggle[0] =
    (HM_DOM) ? document.getElementById(elList[i]) :
    (HM_IE) ? document.all(elList[i]) :
    document.layers[elList[i]];
              break;
        }
        for(var j=0; j<ElementsToToggle.length; j++) {
            var theElement = ElementsToToggle[j];
            if(!theElement) continue;
            if(HM_DOM||HM_IE) {
              theElement.style.visibility =
                  show ? "inherit" : "hidden";
            } else {
              theElement.visibility =
                  show ? "inherit" : "hide";
            }

        }
      }
      return true;

  }
// -->
</script>
<font face="arial">
<link rel="Stylesheet" href="CSS/menu.css" type="text/css">
<table bordercolor="white" align="left" border="1" cellspacing="0" cellpadding="0" width="16%">
<tr bgcolor="red">
<td><center>
<a href="#" onclick="HM_f_ToggleElementList(false,['td1', 'td2', 'td3', 'td4', 'td5', 'td6', 'td7', 'td8', 'td9', 'td10'],'id'); return false">
<img src="images/leftml.gif" border="0" align="left" vspace="5">
Menu &nbsp;&nbsp;</center></a>
</td>
</tr>

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thanks