This is a very short (and incomplete) introduction how to use XML resp. XUL and CSS with libUFO.
Xul is standardized XML format for describing user interfaces. For more information see http://www.xulplanet.com.
A Xul file describes all GUI elements within one root container (URootPane).
UFO implements a subset of XUL, including most of the standard GUI elements.
There is an example file in the test directory
(test/gui.xul) which shows some of the UFO XUL elements.
You can test it via the test/xul.cpp example code.