code: protected void setDragAndDropMessage() {
  
          if (m_dragAndDropMessage == null) {
              m_dragAndDropMessage = new HTML();
              m_dragAndDropMessage.setStyleName(I_CmsLayoutBundle.INSTANCE.uploadCss().dragAndDropMessage());
              m_dragAndDropMessage.setText(Messages.get().key(Messages.GUI_UPLOAD_DRAG_AND_DROP_DISABLED_0));
          }
          getContentWrapper().add(m_dragAndDropMessage);
          getContentWrapper().getElement().getStyle().setBackgroundColor(
              I_CmsConstantsBundle.INSTANCE.css().notificationErrorBg());
          doResize();
      }
docs: Displays the 'use drag and drop' / 'no drag and drop available' message.<p>