I can provide a manual method for making sure all users have the same preferences, including the homepage (instructions made assuming you use Windows, but probably valid with a few tweaks on just any OS):
In Firefox's menu (if you can't find this, use the Firefox button's options to enable the menu bar - it should make finding the option easier), go to
?>Troubleshooting information.In the first table, Application Basics, click on
Show folder.You should be in the current profile's folder. Here you have all information about the user profile in various files, including download history and all sorts of other things. What you're looking for is
prefs.js. Assuming the home page isn't set to the default about:home, then you should find a line that saysuser_pref("browser.startup.homepage", "http://site.com");or something similar in this file. This is the line you need. Not that you actually need to look at the line.Decide which profile will be the "master" one (I'm not sure it changes anything, actually), and for every other user, browse to the equivalent folder. If you're not sure which one it is, log in as that user and use
Troubleshooting informationto be brought there.Making sure Firefox is not running, delete the
prefs.jsfile of each non-master user and replace it with a symbolic link to the "master" profile. You might need to write down the right folders then do these changes from the administrator account.Making a symbolic link: (Assuming you use Windows)
I personally highly recommend the much easier to use Link Shell Extension to do it all through right-click options, but you can use the command prompt to do it as well. I believe this guide should show you how to do it.
When you are done deleting and replacing all
prefs.jswith symbolic links, effectively every change you make to Firefox's preferences (basically, anything that will appear inabout:config) will always be reflected on every user, because they will all in fact refer to the same file.
I haven't tried the method, so I can't tell for sure, but there's a chance only the "master" account will be able to change preferences, and others won't have the permission to change the file. To change this, you'd need to log in to the "master" account (or probably any administrator account) and edit prefs.js's permissions (Right click > Properties > Security) (in Windows) so that every relevant account can edit it.
If you want to make sure not only the preferences, but all of Firefox is precisely the same on every user, you can do the same manipulation, but instead of linking prefs.js, you'll link the whole profile folder.