               document.documentElement.scrollTop : document.body.scrollTop;               
               y = y + y_displacement;               
               
               // The current y is the current coordinate of the floating element.
               // This should be at the limit the y target coordinate.
               this.current_y += (y - this.current_y)/1.25;
               
               // Add the pixels constant after the values
               // and move the element.
               var px