code: private void prepareTargetContainer(
          I_CmsDropContainer targetContainer,
          I_CmsDraggable draggable,
          Element placeholder) {
  
          String positioning = CmsDomUtil.getCurrentStyle(
              targetContainer.getElement(),
              org.opencms.gwt.client.util.CmsDomUtil.Style.position);
          // set target relative, if not absolute or fixed
          if (!Position.ABSOLUTE.getCssName().equals(positioning) && !Position.FIXED.getCssName().equals(positioning)) {
              targetContainer.getElement().getStyle().setPosition(Position.RELATIVE);
          }
          m_originalIndex = targetContainer.getWidgetIndex((Widget)draggable);
          targetContainer.getElement().insertBefore(placeholder, draggable.getElement());
          targetContainer.getElement().addClassName(I_CmsLayoutBundle.INSTANCE.dragdropCss().dragging());
          CmsDomUtil.showOverlay(draggable.getElement(), true);
          targetContainer.highlightContainer();
      }
docs: Prepares the target container.<p>
  
  @param targetContainer the container
  @param draggable the draggable
  @param placeholder the placeholder