I've almost made a wrong trade twice due to the following mixup:
I see "ASK 0.622" and instinctively go to put my own ASK there, type in the qty and price, and then realize that the button next to it is labeled "BUY", which is not exactly what I wanted to do. Maybe removing the words "ASK" and "BID" or making them much smaller than "BUY" and "SELL" would help? On Bitcoinica, for example, the BUY and SELL buttons are big enough that they draw attention first and there's no confusion.
I did the same thing.
As did I.