var isDOM=document.getElementById?1:0;
var isIE=document.all?1:0;
var isNS4=navigator.appName=='Netscape'&&!isDOM?1:0;
var isIE4=isIE&&!isDOM?1:0;
var isOp=window.opera?1:0;
var isDyn=isDOM||isIE||isNS4;

 isNS4 = (document.layers) ? true : false;
 isIE4 = (document.all && !document.getElementById) ? true : false;
 isIE5 = (document.all && document.getElementById) ? true : false;
 isNS6 = (!document.all && document.getElementById) ? true : false;

function showmenu(divname){
if (isNS4) document.layers[divname].visibility = 'visible';
else if (isIE4 || isIE5) document.all(divname).style.visibility = 'visible';
else if (isNS6) document.getElementById(divname).style.visibility = 'visible';
};
function hidemenu(divname){
if (isNS4) document.layers[divname].visibility = 'hidden';
else if (isIE4 || isIE5) document.all(divname).style.visibility = 'hidden';
else if (isNS6) document.getElementById(divname).style.visibility = 'hidden';
};