var layerRef="null", styleSwitch="null";
function hideLayer(layerName){
layerRef=layerN(layerName);
eval(layerRef+'.visibility="hidden"');
}
function layerN(layerName){
if(document.getElementById) return "document.getElementById(layerName).style"
if(document.all) return "document.all[layerName].style"
if(document.layers) return "document.layers[layerName]"
return null
}