Thanks Shobhit,
Actually i was looking to change the error messages that's the Form Server itself are using it, i found the file inside the Layouts/INC folder, and it's a javascript file contains all the error messages as a javascript variables, and i modefied the error messages, but I believe that this technique is NOT SUPPORTED, and may the future packs and hotfixes can restore my modifications.
Regards,
MAS
MAS