actualy... I don't know what it is...
I recognize the Facebook user by his name.
And then I look up his name in my database SQL to retrieve some data, with Ajax Request.
It works fine.
I have a facebook account with my name.
With that account, I can use Ajax to retrieve information on the SQL, with Chrome, IE and Firefox without pb.
I have another Facebook account, with that account, I have the Ajax Error.
Instead of complete, it fails (I don't know what error, it just respond to the On Error).
In the same time it does the Ajax Request, I display the URL use for the Request in the game. If I copy this URL directly in the explorer, I don't have any error.
So it's not a pb with firefox...
It must come from the facebook account...
I don't really understand it.