var adWindow;
function adWindowCenter(winHeight, winWidth, showpage) {

   var topWindow = ((screen.availHeight / 2) - (winHeight / 2));
   var leftWindow = ((screen.availWidth / 2) - (winWidth / 2));  
   var winStats = "toolbar=no ,location=no ,directories=no ,menubar=no ,scrollbars=1 ,";

   if (navigator.appName.indexOf("Microsoft")>=0) {

   	winStats+= "left=";
   	winStats+= leftWindow.toString();
   	winStats+= ",top=";
   	winStats+= topWindow.toString(); 

   }else{


   	winStats+= "screenX=";
   	winStats+= leftWindow.toString();
   	winStats+= ",screenY=";
   	winStats+= topWindow.toString(); 
   }

   winStats+= ",width=";
   winStats+= winWidth.toString();
   winStats+= ",height=";
   winStats+= winHeight.toString();
  
   
   PopUpKiller();

   adWindow = window.open(showpage,"_blank",winStats); 
   adWindow.focus();
   
   
}

function PopUpKiller() {
   if (adWindow && !adWindow.closed) {
	adWindow .close(); 
   }
}