I'm working with a tree style navigation that I found at DynamicDrive and I want to the ability to close an open branch when another is selected. The code is short and sweet, but the syntax is a bit over my head I think. Does anyone know how I would go about it?

Code:
<html>
<head>
<title>Untitled Document</title>

<script language="JavaScript1.2">
<!--

//Smart Folding Menu tree- By Dynamic Drive (rewritten 03/03/02)
//For full source code and more DHTML scripts, visit http://www.dynamicdrive.com
//This credit MUST stay intact for use

var ns6=document.getElementById&&!document.all
var ie4=document.all&&navigator.userAgent.indexOf("Opera")==-1

function checkcontained(e){
var iscontained=0
cur=ns6? e.target : event.srcElement
i=0
if (cur.id=="foldheader")
iscontained=1
else
while (ns6&&cur.parentNode||(ie4&&cur.parentElement)){
if (cur.id=="foldheader"||cur.id=="foldinglist"){
iscontained=(cur.id=="foldheader")? 1 : 0
break
}
cur=ns6? cur.parentNode : cur.parentElement
}

if (iscontained){
var foldercontent=ns6? cur.nextSibling.nextSibling : cur.all.tags("UL")[0]
if (foldercontent.style.display=="none"){
foldercontent.style.display=""
}
else{
foldercontent.style.display="none"
}
}
}

if (ie4||ns6)
document.onclick=checkcontained

//-->
</script>
</head>

<body>
<font face="Verdana">

<ul>
   <li id="foldheader">News</li>
   <ul id="foldinglist" style="display:none">
      <li><a href="http://www.cnn.com">CNN</a></li>
      <li><a href="http://www.abcnews.com">ABC News</a></li>
      <li><a href="http://www.news.bbc.co.uk">BBC News</a></li>
   </ul>

   <li id="foldheader">Webmaster</li>
   <ul id="foldinglist" style="display:none">
      <li><a href="http://www.dynamicdrive.com">Dynamic Drive</a></li>
      <li><a href="http://www.javascriptkit.com">JavaScript Kit</a></li>
      <li><a href="http://www.freewarejava.com">Freewarejava.com</a></li>
   </ul>

   <li id="foldheader">Nested Example</li>
   <ul id="foldinglist" style="display:none">
      <li><a href="http://www.dynamicdrive.com">outer 1</a></li>
      <li><a href="http://www.dynamicdrive.com">outer 2</a></li>
      <li id="foldheader">Nested</li>
      <ul id="foldinglist" style="display:none">
         <li><a href="http://www.dynamicdrive.com">nested 1</a></li>
         <li><a href="http://www.dynamicdrive.com">nested 2</a></li>
      </ul>
      <li><a href="http://www.dynamicdrive.com">outer 3</a></li>
      <li><a href="http://www.dynamicdrive.com">outer 4</a></li>
   </ul>
</ul>

</font>

<p align="center"><font face="Arial" size="-2">Free DHTML scripts provided by<br>
<a href="http://www.dynamicdrive.com">Dynamic Drive</a></font></p>
</body>
</html>