how to disable compiz fusion temporarily?

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http://www.debianhelp.org – I found a strange thing that when i upgrade compiz to compiz fusion (my system is testing). I can not figure out how it is launched when i login. Previously, there is a start up entry in Gnome Sessions. Now, even i delete that entry, compiz fusion still starts up each time.i neither want to start up it everytime, nor to uninstall compiz fusion. Does anybody know how to disable compiz fusion temporarily (HowTos)