code: protected void showError() {
  
          if (hasError()) {
              m_label.getElement().getStyle().clearDisplay();
              CmsFadeAnimation.fadeIn(m_label.getElement(), new Command() {
  
                  /**
                   * @see com.google.gwt.user.client.Command#execute()
                   */
                  public void execute() {
  
                      // noop
                  }
              }, 300);
          }
      }
docs: Shows the error.<p>