While the Dow Jones Industrial Average turned losses around Friday, with most investors taking weak economic news in stride, ad stocks fell. Investors in media and ad holding company stocks are anticipating acknowledgement of a rebound, said Michael Russell, media analyst at Morgan Stanley Dean Witter. “There’s a reluctance on the part of companies to do that until the recovery is in full swing,” he said. “No one wants to stick their neck out and find that they’ve yelled ‘Yay!’ prematurely.” On the Big Board, Omnicom’s shares dropped 2.9 percent to close at $78.19, while IPG fell 4.1 percent to $14.80. British holding company WPP, trading as American Depository Receipts on the Nasdaq, slid 4.3 percent to $44.14.