Stocks partied Friday as if the previous session’s sell-off was just one big misunderstanding. The Nasdaq, S&P 500 and Dow Jones industrial average each danced 2.1% higher. Small caps, though, lagged with the S&P 600 gaining only 1%. The IBD 50 jumped 2.5%. Volume ran higher most of the session but then faded in the final two hours to finish lower for the day.