code: function() {
              YAHOO.log('Creating Shim Element', 'info', 'DragDropMgr');
              var s = document.createElement('div');
              s.id = 'yui-ddm-shim';
              if (document.body.firstChild) {
                  document.body.insertBefore(s, document.body.firstChild);
              } else {
                  document.body.appendChild(s);
              }
              s.style.display = 'none';
              s.style.backgroundColor = 'red';
              s.style.position = 'absolute';
              s.style.zIndex = '99999';
              Dom.setStyle(s, 'opacity', '0');
              this._shim = s;
              Event.on(s, "mouseup",   this.handleMouseUp, this, true);
              Event.on(s, "mousemove", this.handleMouseMove, this, true);
              Event.on(window, 'scroll', this._sizeShim, this, true);
          }
docs: This method will create a shim element (giving it the id of yui-ddm-shim), it also attaches the mousemove and mouseup listeners to it and attaches a scroll listener on the window
  @private
  @method _sizeShim
  @static