The stock market erased earlier gains and fell by early afternoon Wednesday as home sales dropped and natural gas prices slid. Oil and natural gas stocks also fell, as did technology stocks. X The Nasdaq composite fell 0.7% while the S&P 500 dropped 0.4%. The Dow Jones Industrial Average dipped 0.4%. The small-cap Russell 2000 index fell 1%. The Nasdaq composite and S&P 500 are trading at their lowest levels since early November and threaten to undercut those lows. Volume fell on the Nasdaq and the NYSE vs. the same time on Tuesday. Volume this week is expected to be...