Stocks are opening mostly slightly higher on Wall Street, but the market is still headed for its worst week since early June. The Dow Jones industrial average is up 36 points at 13,362 shortly after the opening bell Friday. Wal-Mart Stores was the biggest gainer in the Dow following an analyst upgrade, up 73 cents at $75.74. The Standard & Poor's 500 index edged up one point to 1,434 and the Nasdaq composite was off two points at 3,047. The S&P is headed for a weekly loss of nearly 2% following three down days this week. Wells Fargo fell 4%, giving up $1.38 to $33.80, after its revenue fell short of what analysts were expecting.