When the user exists XFCE the window manager will ask the user if it should save the session such that it may be restored next time.
This feature only seems to work partially, sometimes windows will spawn out of place, even though the window was not moved, and sometimes windows will simply fail to spawn. Some programs, WINE in particular are never started automatically in this manner.

Why does this happen? Why does not all programs get started? What file(s) control what programs to start, where to start them (x and y coordinates, virtual desktop)?
How can I make XFCE spawn programs on a dual monitor setup? For some reason XFCE only wants to spawn programs on the "first" or "master" monitor.