Yahoo co-founder Jerry Yang is stepping down as CEO, ending one of the most turbulent periods in the dot-com company’s history. Yang’s tenure was marked by his refusal to sell Yahoo to Microsoft  for $47.5 billion — more than triple Yahoo’s current market value. A backup plan to forge an advertising partnership with Google collapsed earlier this month when Google walked away from the deal to avoid an antitrust battle with the U.S. Justice Department. Yang, who will revert to “Chief Yahoo,” will stay on until a successor is named. Sue Decker, Yahoo’s president, is one of the leading candidates to replace Yang.  (Here is the official release announcing Yang’s departure as CEO.)