Stocks erased most of 1%-plus gains Thursday, indicating apprehension ahead of the key jobs report on Friday. The Nasdaq fell nearly 0.4% after being up as much as 1.1%. The S&P 500 and Dow Jones industrial average saved only 0.1% of their advances. Volume was lower on the Nasdaq and NYSE, according to unconfirmed figures. For a couple of weeks, the 50-day moving averages of the S&P and Dow have been below the 200-day moving averages.