How can I add my startup programs to gnome session system wide?

[Rocky Zhang <rocky userful com>]

Hi,

I know I can use "gnome-session-properties" to add startup programs for
each user. I'd like to add my startup programs to gnome-session system
wide (take effect for every gnome session whatever which user log in).
Is there any way to realize it by NOT using gnome-session-properties for
every user?

Thanks.

Rocky