Vikram!

Reports from CNBC and our own sources suggest that it was a Citigroup (C) trader that accidentally entered a sell BILLION-size sell trade, when they meant to do million.

Since the market came back and only ended down over 3%, all the focus now is on what happened. There's going to be an investigation into Proctor & Gamble (PG) trading, Accenture (ACN) and the market as a whole.

In addition to the fat finger error, there will be a lot of talk about high-frequency trading and its affect.