var popup = false;
function openPopup(url, name, features){   
  if (typeof(popup) == 'object' && popup.closed != true && popup.name == name){
    popup.focus();
  }else {
    try {
      popup.close();
    }catch(e){
      popup = false;
    }
    popup = window.open(url, name, features, 'false');
  }
}