code: public static int getRelativeY(int y, Element target) {
  
          return (y - target.getAbsoluteTop()) + /* target.getScrollTop() +*/target.getOwnerDocument().getScrollTop();
      }
docs: Gets the vertical position of the given y-coordinate relative to a given element.<p>
  
  @param y the coordinate to use
  @param target the element whose coordinate system is to be used
  
  @return the relative vertical position
  
  @see com.google.gwt.event.dom.client.MouseEvent#getRelativeY(com.google.gwt.dom.client.Element)