10:15 a.m. Update: Stocks opened lower Friday, giving back a chunk of Thursday's big gains. The S&P 500 and Dow both dipped 0.6%. The Nasdaq fell 0.4% and the NYSE composite 1%. Volume dipped across the board. Trading declined 17% on the NYSE compared to the same period Thursday. It slid 24% on the Nasdaq. In economic news, consumer sentiment slipped in October. The Reuters/University of Michigan Survey of Consumers