var nn4 = (document.layers);
var nn6 = (document.getElementById && !document.all);
var ie4 = (document.all && !document.getElementById);
var ie5 = (document.all && document.getElementById);
var divCurrent=0;

function popup(divNumber) {
 var divName='popup';
 if(divCurrent!=0) {
   var divHide=divName+divCurrent;
   if (nn4) document.layers[divHide].visibility='hide';
   else if (nn6) document.getElementById(divHide).style.visibility='hidden';
   else if (ie4) document.all(divHide).style.visibility='hidden';
   else if (ie5) document.getElementById(divHide).style.visibility='hidden';
 }
 if(divNumber!=0) {
   var divShow=divName+divNumber;
   if (nn4) document.layers[divShow].visibility='show';
   else if (nn6) document.getElementById(divShow).style.visibility='visible';
   else if (ie4) document.all(divShow).style.visibility='visible';
   else if (ie5) document.getElementById(divShow).style.visibility='visible';
   // else location="oldbrowser.htm";
 }
 divCurrent=divNumber;
}