facebook adding ? to my URL's

[eluser]FumarMata[/eluser]
Hello

I'm having a problem with a site and facebook. When people shares it in their walls or using my app, Facebook adds "?ref=nf" at the end

http://www.example.com/?ref=nf

and that makes my site show a 404 error - not found, probably related to the disallowed characters in the URL.

As that's the only place where the ? is added, do you know some way to redirect that to my homepage without having to allow special characters? I am a bit scared of the warning message in config.php

Code:

/*
|--------------------------------------------------------------------------
| Allowed URL Characters
|--------------------------------------------------------------------------
| .....
| As a security measure you are STRONGLY encouraged to restrict URLs to
| as few characters as possible.  By default only these are allowed: a-z 0-9~%.:_-
|.....|
| DO NOT CHANGE THIS UNLESS YOU FULLY UNDERSTAND THE REPERCUSSIONS!!
|
*/

Thanks