Stocks shook off early weakness Wednesday and rallied to post moderate gains in mixed volume. NYSE volume was higher and Nasdaq lower, according to preliminary data. The Nasdaq rose 0.4%, while the S&P 500 and the Dow Jones industrial average gained 0.5% in the stock market today. Facebook (FB) was erratic after the close, but was mostly lower. It reported Q1 earnings after the bell of 42 cents a share vs. estimates of 40 cents.