Perhaps the big story in the market was the very weak bank trading. Financials slumped ~1.4% overall and the BKX was down ~1.6% (note that the BKX broke down through its 50dayAM for the firs time since Nov '12). The Citi article from the FT this weekend didn't help but sentiment in general is becoming pretty gloomy (NIMs won't expand as quickly thanks to the Fed, trading trends appear to be softer than expected, reserve releases and opex cuts can't continue forever, regulatory scrutiny is only worsening, etc). Away from financials, one of the other big trends was selling/profit taking in a bunch of the best-performing "momentum" stocks (many of them in internet and biotech) - BIIB, CELG, GILD, RGEN, YHOO, GOOG, NFLX, etc (there really wasn't a specific fundamental "reason" behind the action in these names other than people looking to lock in profits ahead of the quarter and month end).
Here's the report from FT about how Citi's trading revenue has dropped.
Anyway, one day of market action isn't a big thing, still it's interesting that the "no taper" rally has totally evaporated.