Is it permissible to purchase from an online auction site—such as "bidz"—using a prepaid card from Al-Ahli Bank, and is it permissible to trade the commodity after possessing it if the purchase is lawful, and what should a person do with commodities they have acquired and paid for if the purchase is unlawful?

It is impermissible to purchase gold and silver from the website due to the absence of the immediate, on-the-spot exchange (taqabud) which is a condition for their transaction. However, it is permissible to purchase other products besides gold and silver. It is also permissible to buy with a pre-paid Visa card. There is no harm in trading a commodity purchased from the website after acquiring ownership of it and moving it from the seller's place. As for one who purchased gold and silver from it out of ignorance, Allah will forgive him. But if he was aware, he must repent.