Object.extend(Draggable.prototype, {
 startDrag: function(event) {
    this.dragging = true;
    
    if(this.options.zindex) {
      this.originalZ = parseInt(Element.getStyle(this.element,'z-index') || 0);
      this.element.style.zIndex = this.options.zindex;
    }
    
    if(this.options.ghosting) {
      this._clone = this.element.cloneNode(true);
      Position.absolutize(this.element);
      this.element.parentNode.insertBefore(this._clone, this.element);
    }
    
    Draggables.notify('onStart', this, event);
    if(this.options.starteffect) this.options.starteffect(this.element);
    if(this.options.dragStart) this.options.dragStart(this.element); // NOTE: Added new callback for dragStart
  }})