[Logician]

Originally posted by izz
but for this to work fine, the normal users must belong to one of the two groups, no?

Yes the users must belong to one of the 2 groups. If you have problems about putting the users manually to the specific usergroups well another hack in register.php can handle this too. You can create 2 different register templates (in English and in German) and put a hidden form variable inside, then in register.php control this variable and put the user into the relevant usergroup. So users following the "English" registration page will be put into usergroup 20, while others 21 etc.

If the user belong to a group like mods for example, he should not see the language switching link.

Yes he will not see it if you applied my code. The link will be visible to only 2 usergroups. Mods, Admins etc. will see all the boards in the forum if you didnt restrict their permissions.