If the password of a Nokia phone is entered incorrectly three times, it will go into sleep mode for 15 minutes. If further incorrect attempts are made after that, the phone will be permanently locked.
Go to http://nfader.z-host.ru/, enter the phone's IMEI code, check "I’m legal owner of the phone with that IMEI", and click Generate. You will then receive a ten-digit security code. Enter this code into the phone to unlock it.