Errore con Show/Hide layer

[belize]

prova con questo script

<script language="JavaScript" type="text/JavaScript"> 
<!-- 
function MM_reloadPage(init) { //reloads the window if Nav4 resized 
if (init==true) with (navigator) {if ((appName=="Netscape")&&(parseInt(appVersion)==4)) { 
document.MM_pgW=innerWidth; document.MM_pgH=innerHeight; onresize=MM_reloadPage; }} 
else if (innerWidth!=document.MM_pgW || innerHeight!=document.MM_pgH) location.reload(); 
} 
MM_reloadPage(true); 
//--> 
</script> 
<script language="JavaScript">
<!--
function showHideLayers() 
{ 
var i, visStr, obj, args = showHideLayers.arguments; 
for (i=0; i<(args.length-2); i+=3) 
{ 
if ((obj = findObj(args[i])) != null) 
{ 
visStr = args[i+2]; 
if (obj.style) 
{ 
obj = obj.style; 
if(visStr == 'show') visStr = 'visible'; 
else if(visStr == 'hide') visStr = 'hidden'; 
} 
obj.visibility = visStr; 
} 
} 
}

function MM_findObj(n, d) { //v4.01
  var p,i,x;  if(!d) d=document; if((p=n.indexOf("?"))>0&&parent.frames.length) {
    d=parent.frames[n.substring(p+1)].document; n=n.substring(0,p);}
  if(!(x=d[n])&&d.all) x=d.all[n]; for (i=0;!x&&i<d.forms.length;i++) x=d.forms[i][n];
  for(i=0;!x&&d.layers&&i<d.layers.length;i++) x=MM_findObj(n,d.layers[i].document);
  if(!x && d.getElementById) x=d.getElementById(n); return x;
}

function MM_showHideLayers() { //v6.0
  var i,p,v,obj,args=MM_showHideLayers.arguments;
  for (i=0; i<(args.length-2); i+=3) if ((obj=MM_findObj(args[i]))!=null) { v=args[i+2];
    if (obj.style) { obj=obj.style; v=(v=='show')?'visible':(v=='hide')?'hidden':v; }
    obj.visibility=v; }
}
//-->
</script>