User Session Startup Configuration
Several configuration files are processed during a user's X session startup.
.xprofile is sourced by gdm at the very start of the X session initialization. It is an appropriate place to set environment variables that should affect the X initialization process including keyboard layout and language initialization, although note that many values may be overridden.
.xsessionrc is sourced by 40x11-common_xsessionrc during the start of the X session. It is intended for setting session-wide environment variables that should apply to all apps, such as locale information. Remember that for most shells you will have to explicitly export the variable for it to take effect in your session.
.gnomerc is sourced by 55gnome-session_gnomerc after X is initialized and the window manager has been started, while GNOME is setting itself up. It is appropriate for desktop-specific settings, although note that this runs before the user's dbus session bus, xdg, and ssh-agent have been started, so anything requiring these should be placed in Startup Applications instead.