http://www.xulplanet.com/tutorials/xultu/grids.html http://www.xulplanet.com/reference/elemref/ref_grid.html A grid is an element that contains both rows and columns elements. It is used to create a grid of elements. Both the rows and columns are displayed at once although only one will typically contain content, while the other may provide size information. Whichever is last in the grid is displayed on top.