-call card issuer for approval (usually means a change spending habit and they want to verify the customer)
-invalid card (usually just computer error reading the card)
-"decline" (no further explanation)
-"decline sale and keep card" (stolen credit card)
-"insufficent funds" (only on atm/check-card)
in general, declined sales on a credit card usually return a specific error. Some registers only report success for failure, some report reasons. For privacy reasons, and you save you embarracement from other customers, cashiers will almost always say "all it says is decline."
Checks, on the other hand... If your check is declined, it's because you passed a bad one somewhere and your account is currently blacklisted by the store's check clearing network. There is no real-time look-up of your account balance when the scanner reads the check, contrary to what some people believe.
Limecat is not pleased.