http://www.xulplanet.com/tutorials/xultu/scroll.html http://www.xulplanet.com/reference/elemref/ref_scrollbar.html When a container contains contents which are larger that the size of the content, scroll bars may be placed at the side of the container to allow the user to scroll around in the container. The scroll bar may also be used independently when a numeric value or percentage needs to be selected by the user. The user can adjust the position of the scroll bar by clicking arrows on either end of the scroll bar or by dragging the scroll bar thumb around. The current position of the scrollbar, which ranges from 0 to the value of the maxpos attribute. The default value is 0. The amount that the value of the curpos attribute changes by when the scroll bar arrows are clicked. The default value is 1. The maximum position of the scrollbar. The default value is 100. The amount that the value of the curpos attribute changes by when the tray of the scroll bar is clicked. The tray is the area in which the scroll bar thumb moves along. The default value is 10.