Stocks posted gains for the fourth day on Tuesday. The Nasdaq had its biggest percentage gain since October, while the S&P 500 marked its best day in two months in what investors believe could be continued short-term buying from deeply oversold levels. Volume was lighter than normal, however, with just 6.69 billion shares traded on the New York, Nasdaq and New York Stock Exchange (NYSE) Amex exchanges, compared with a daily average of 7.58 billion. The Dow Jones industrial average rose 109.63 points, or 0.91 percent, to 12,190.01 at the close. The Standard & Poor's 500 Index gained 17.16 points, or 1.34 percent, to 1,295.52. The Nasdaq Composite Index climbed 57.60 points, or 2.19 percent, to 2,687.26. The Nasdaq ended Tuesday's session above its 50- and 200-day moving averages, for the first time since May 31. The Dow and the S&P 500 finished last week with gains after six weeks of declines. The Nasdaq, however, ended the week in the minus column. The S&P 500 is down 5 percent since its May 2 high. After nearing its 200-day moving average Monday, the S&P 500 rebounded solidly above the level.