Error in the registration..

[idan0401]

Part tell me that they receive Tshgiaa this : Invalid Referrer Specified

What this says? How settle?

Thank you to the helpful

[Marco van Herwaarden]

They enter a username as referrer that does not exist.

[idan0401]

How I settle this?
Appears also this error :
Invalid referrer specified

[Dismounted]

Tell them not to put a referrer when registering.