Wall Street opens lower after two-day rally

Wall Street opened lower on Friday, suggesting investors were wary of taking big positions into the weekend after days of tumultuous trading that featured both the market's worst day in four years and biggest two-day gain since the financial crisis.

The Dow Jones industrial average fell 76.74 points, or 0.46 percent, to 16,578.03, the S&P 500 lost 7.1 points, or 0.36 percent, to 1,980.56 and the Nasdaq composite dropped 18.99 points, or 0.39 percent, to 4,793.72.