var ie4 = (document.all) ? true : false; 
var ns4 = (document.layers) ? true : false; 
var ns6 = (document.getElementById && !document.all) ? true : false; 
function hidelayer(lay) { 
if (ie4) {document.all[lay].style.visibility = "hidden";} 
if (ns4) {document.layers[lay].visibility = "hide";} 
if (ns6) {document.getElementById([lay]).style.display = "none";} 
} 
function showlayer(lay) { 
if (ie4) {document.all[lay].style.visibility = "visible";} 
if (ns4) {document.layers[lay].visibility = "show";} 
if (ns6) {document.getElementById([lay]).style.display = "block";} 
} 
function writetolayer(lay,txt) { 
if (ie4) { 
document.all[lay].innerHTML = txt; 
} 
if (ns4) { 
document[lay].document.write(txt); 
document[lay].document.close(); 
} 
if (ns6) { 
over = document.getElementById([lay]); 
range = document.createRange(); 
range.setStartBefore(over); 
domfrag = range.createContextualFragment(txt); 
while (over.hasChildNodes()) { 
over.removeChild(over.lastChild); 
} 
over.appendChild(domfrag); 
   } 
} 

function switchMap (url)  { 
	document.images["map"].src = url; 
}