Transactions Tab

Very left column -

• Check mark - the transaction has been received and has matured (10+ confirmations needed for rewards)
• Circle - shows approximation of confirmations remaining for maturity
• Question mark - indicates the reward is of an orphan block (natural occurrence when someone won the same block as you but propagated the block quicker to the blockchain) or an error ocurred during the transactions (conflicts with the transaction, usually ocurred when you have not enought connections with the network and you are forking it accidentally) (See chains & solutions faq)

Double-click on a transaction to see further details about it: