var popupObj = null;

function popupOpen(theURL,winName,features, myWidth, myHeight, isCenter) 
{ //v3.0
   if(window.screen && isCenter){
     var myLeft = (screen.width-myWidth)/2;
     var myTop = 0;
     if (features!='') features+=',';
     features+='left='+myLeft+',top='+myTop;
   }
   if (features!='') features+=',';
   features+='width='+myWidth+',height='+myHeight;
   popupObj = window.open(theURL,winName,features);
   popupObj.focus();
}

function popupClose() {
   if (popupObj) popupObj.close();
}