Wall Street Nervous After 'Flash Crash' Thursday

The Dow Jones Industrial Average opened lower Friday morning as investors reeled from Thursday's "flash crash" on Wall Street, which saw the biggest one-day plunge ever in the Dow. Stocks took a sudden, breathtaking plunge in a massive sell-off, with the Dow falling nearly 1,000 points at one point in the afternoon -- before rebounding just as quickly. It closed down some 348 points, at 10,520.32. Sources told ABC News that a trading error at Citigroup may have contributed to the abrupt drop,...Full Story