http://www.xulplanet.com/tutorials/xultu/splitter.html http://www.xulplanet.com/reference/elemref/ref_splitter.html An element which should appear before or after an element inside a container. When the splitter is dragged, the sibling elements of the splitter are resized. If a grippy in placed inside the splitter, one sibling element of the splitter is collapsed when the grippy is clicked. Determines which side of the splitter is collapsed when its grippy is clicked. If this attribute is not specified, the splitter will not cause a collapse. You should put a grippy element inside the splitter when it is used for collapsing. No collpasing occurs. When the grippy is clicked, the element immediately before the splitter in the same parent is collapsed so that its width or height is 0. When the grippy is clicked, the element immediately after the splitter in the same parent is collapsed so that its width or height is 0. This attribute indicates which element to the right or below the splitter should be resized when the splitter is repositioned. The element immediately to the right or below the splitter resizes. The element that is the farthest away from the splitter to the right or below the splitter resizes. The elements to the right or below the splitter do not change size (unless they are flexible) when the splitter is dragged, but instead the entire container changes size. This attribute indicates which element to the left or above the splitter should be resized when the splitter is repositioned. The element immediately to the left or above the splitter resizes. The element that is the farthest away from the splitter to the left or above the splitter resizes. Indicates whether the splitter has collapsed content or not. This attribute will be updated automatically as the splitter is moved, and is generally used in a stylesheet to apply a different appearance for each state. The content either before or after the splitter, depending on the value of the collapsed attribute, is currently displayed. The content either before or after the splitter is collapsed and is not visible. The user is current adjusting the position of the splitter, typically by dragging it with the mouse. This splitter is intended to be used in tree columns (in-between treecol elements). The splitter will be drawn with no width so that it isn't visible, however, the columns may still be resized.