How can we change the default iceweasel startup / home page?

[Petter Reinholdtsen <pere@hungry.com>]

How can we change the default iceweasel startup / home page (the one
shown when iceweasel is started for the first time), to be

  http://www/

for all networked installations and

  http://www.skolelinux.org/

for all standalone installations?

Happy hacking,
-- 
Petter Reinholdtsen