Does anybody know how to automatically start firefox in full screen mode pointing to

Does anybody know how to automatically start firefox in full screen mode pointing to a specific web address after the BBB boots-up?
Any help appreciated.

I followed this start-up process as on the link provided http://stackoverflow.com/questions/11152657/angstrom-start-up-processes-beaglebone
but it would not work…
after: systemctl -a
I got: myScript.service failed
As Steven pointed this is not what I want to do anyway because I have to make sure X is running before I call firefox. Angstrom is using gdm.service, so it is not simple startx script.
How can get into the GDM startup files?

Try looking at this, http://www.acm.uiuc.edu/workshops/cool_unix/xinitrc.html

{Joining in here as I am working on this with Marek} The way we do this normally on MOST full Linux distros is to call:

firefox -display :0

Then we can call it as a script from any session context.

The problem has been that we don’t know the name of the display. The xset commands (which require the display name) don’t work either.