What were you doing (or trying to do):
Buying food via a trade offer
What happened (describe thoroughly please): I clicked to buy all of the food in a particular offer and it was being sloooooooow so I clicked a couple more times. When the page finally loaded, the food was credited to my nation and the money deducted from my nation, but the exact same trade offer was still displaying. In other words, the seller had not relisted a new offer with the same terms; it was the very same offer (with the same timestamp from many minutes earlier). In fact, the amount of food and money credited to and deducted from my account, respectively, was double the offer, meaning that I had somehow managed to buy the same offer twice. It also gave me an error message saying that I didn't have enough funds for the transaction, so I assume it would have allowed me to buy the offer over and over again if I had had enough money for it.
The offer in question is no longer displaying though. Sorry, I didn't get a screenshot of it.