If anybody needs this in the future.
Firefox stores its default configuration in /usr/lib/firefox-x.x.x/defaults/preferences/firefox.js
also look at other files in this and the /usr/lib/firefox-x.x.x/defaults/profile directory

I also found out how to prevent users from changing their settings. Its all explained at the folowing link:
http://ubuntuforums.org/showthread.php?t=812832

BR

On Fri, Nov 6, 2009 at 3:40 PM, James Pearson <james-p@moving-picture.com> wrote:
Janez Kosmrlj wrote:
> Hi,
> I would like to change default settings in firefox (homepage and some
> security settings) and I would like to do this system wide for all users.
> Does anybody know where firefox has it's default configuration files.

I use the method described at:

<http://managingosx.wordpress.com/2008/08/18/firefox-default-settings/>

It's aimed at firefox on MacOS - but works fine with firefox on Linux

James Pearson
_______________________________________________
CentOS mailing list
CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos