What is C V V / CID?  
MasterCard/Visa CVV   If you are using a MasterCard or Visa to pay for this purchase, you must provide the 3-digit CVV (Customer Verification Value) which can be found after the account number on the back of your card.
American Express CID   If you are using an American Express card to pay for this purchase, you must provide the 4-digit CID (Confidential Identifier Number) which can be found on the front-right section of your card above the account number.