Javascript switch menu please help

I have this great script which I downloaded from http://getElementById.com

The problem is very simple - my links actually load new pages, and resets the menu. I would like the submenus to stay visible on the new page. I am not very familiar with javascript, and I was wondering if someone could help me!
I've included the script and also a sample from the html body.

<script type="text/javascript">
/*
Script made by Martial Boissonneault © 2001-2003 http://getElementById.com/
This script may be used and changed freely as long as this msg is intact
Visit http://getElementById.com/ for more free scripts and tutorials.
*/
function SwitchMenu(obj){
if(document.getElementById){
var el = document.getElementById(obj);
var ar = document.getElementById("cont").getElementsByTagName("DIV");
if(el.style.display == "none"){
for (var i=0; i<ar.length; i++){
ar.style.display = "none";
}
el.style.display = "block";
}else{
el.style.display = "none";
}
}
}
function ChangeClass(menu, newClass) {
if (document.getElementById) {
document.getElementById(menu).className = newClass;
}
}
document.onselectstart = new Function("return false");

</script>

from the body....

<div id="cont">
<p id="menu1" class="menuOut" onclick="SwitchMenu('sub1')" onmouseover="ChangeClass('menu1','menuOver')" onmouseout="ChangeClass('menu1','menuOut')"><a href="main.php"><img src="button_home.gif"></a></p>


<p id="menu2" class="menuOut" onclick="SwitchMenu('sub2')" onmouseover="ChangeClass('menu2','menuOver')" onmouseout="ChangeClass('menu2','menuOut')"><img src="button_info.gif"></a></p>
<div class="submenu" id="sub2" style="display:none;">