tree menu, images don't work

[wxdqz]

i got this script from javafiles - it works, but the images aren't working, any help would be much appriciated,
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head stuff
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<script language="javascript">
<!--
var Open = ""
var Closed = ""

function preload(){
if(document.images){
Open = new Image();
Closed = new Image();
Open.src = "open.gif";
Closed.src = "closed.gif";
}
}

function showhide(what,what2){
if (what.style.display=='none'){
what.style.display='';
what2.src=Open.src
}
else{
what.style.display='none'
what2.src=Closed.src
}
}
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code on page
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