Economy and bank worries send stocks lower
* Shares of major banks, including Bank of America and Citigroup , widened their sell-off as investors' mood darkened.
* The Dow Jones industrial average slid 223.65 points, or 2.82 percent, to 7,715.88. The Standard & Poor's 500 Index fell 23.36 points, or 2.80 percent, to 810.38. The Nasdaq Composite Index lost 30.02 points, or 1.96 percent, to 1,500.48.
* The slide took the benchmark S&P 500 index down 12 percent since the start of 2009.
(Reporting by Deepa Seetharaman; Editing by Jonathan Oatis)