code: public void openPageOrWarn(String link, String target, final String warning) {
  
          m_windowExtension.open(link, target, new Runnable() {
  
              public void run() {
  
                  Notification.show(warning, Type.ERROR_MESSAGE);
              }
          });
      }
docs: Tries to open a new browser window, and shows a warning if opening the window fails (usually because of popup blockers).<p>
  
  @param link the URL to open in the new window
  @param target the target window name
  @param warning the warning to show if opening the window fails