It was an odd session Friday. Stocks slid in mixed volume, adding a distribution day to the Nasdaq. The NYSE composite sliced off 1.6%, the S&P 500 1.2%, the Dow 1.1% and the Nasdaq 0.5%. Volume fell on the NYSE and rose on the Nasdaq. But trading in Amazon (AMZN) and Microsoft (MSFT) alone — the two stocks soared on strong earnings — topped 260 million shares. That more than accounted for the higher Nasdaq volume, softening the significance of