Salve, navigando tra le risorse javascript di questo sito mi sono imbattuto in un comodissimo menu ad albero fatto in javascript.
Il problema è il seguente:

Non riesco a capire per quale motivo il codice seguente funziona correttamente su Internet Explorer 6 e non ne vuol sapere di funzionare su Mozilla Firefox 2.0.0.11.

codice:
<html>
<head> 
<script language="JavaScript1.2">

<!--



var head="display:''"

img1=new Image()

img1.src="img/fold.gif"

img2=new Image()

img2.src="img/open.gif"



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=""

cur.style.listStyleImage="url(img/open.gif)"

}

else{

foldercontent.style.display="none"

cur.style.listStyleImage="url(img/fold.gif)"

}

}

}



if (ie4||ns6)

document.onclick=checkcontained



//-->

</script>
</head>
<body>
<ul id="foldinginit">
<li id="foldheader">Fallimentare<ul id="foldinglist" style="display:none" style=&{head};>[/list]
<li id="foldheader">Civile<ul id="foldinglist" style="display:none" style=&{head};>
	<li id="foldheader">Famiglia<ul id="foldinglist" style="display:none" style=&{head};>[/list]
	<li id="foldheader">Successioni<ul id="foldinglist" style="display:none" style=&{head};>[/list]
	<li id="foldheader">Risarcimento<ul id="foldinglist" style="display:none" style=&{head};>[/list]
	<li id="foldheader">Contratti<ul id="foldinglist" style="display:none" style=&{head};>[/list]
	<li id="foldheader">Obbligazioni<ul id="foldinglist" style="display:none" style=&{head};>[/list][/list]
<li id="foldheader">Penale<ul id="foldinglist" style="display:none" style=&{head};>[/list]
<li id="foldheader">Amministrativo<ul id="foldinglist" style="display:none" style=&{head};>
	<li id="foldheader">Appalti<ul id="foldinglist" style="display:none" style=&{head};>[/list]
	<li id="foldheader">Risarcimento<ul id="foldinglist" style="display:none" style=&{head};>[/list]
	<li id="foldheader">Edilizia<ul id="foldinglist" style="display:none" style=&{head};>[/list]
	<li id="foldheader">Urbanistica<ul id="foldinglist" style="display:none" style=&{head};>[/list][/list]
<li id="foldheader">Tributario<ul id="foldinglist" style="display:none" style=&{head};>[/list]
<li id="foldheader">Societario<ul id="foldinglist" style="display:none" style=&{head};>[/list][/list]
</body>
</html>
Grazie per l' attenzione