// whenever the dragged item moves, update the positions of all
          // the affected items, updating their position with the same relative
          // offset.
          drag: function(ev, ui) {
            ids = dragGroups[ui.helper[0].id];          
            for (var i = 0; i < ids.length; i++) {
              if (ids[i] != ui.helper[0].id) {
                $('#' + ids[i]).css('top',
                                $('#'+ids[i]).data("top0") + ui.position.top);
                $('#' + ids[i]).css('left', 
                                $('#'+ids[i]).data("left0") + ui.position.left);              
              }
            }
          },