function popup(url, w, h) {
   var dx = Math.round((screen.availWidth - w) / 2);
   var dy = Math.round((screen.availHeight - h) / 2);
   return window.open(url,'','width='+w+', height='+h+', left='+dx+', top='+dy+', toolbar=no, statusbar=no, scrollbars=yes, resizable=yes, menubar=no');
}

function popup_custom(url,w,h,params) {
   var dx = Math.round((screen.availWidth - w) / 2);
   var dy = Math.round((screen.availHeight - h) / 2);
   return window.open(url,'','width='+w+', height='+h+', left='+dx+', top='+dy+','+params);
}

function stopEvent(e) {
   if (e.stopPropagation) e.stopPropagation();
   else window.event.cancelBubble = true;
}

if(!self.go) function go(url) {
   window.location = url;
   return true;
}