Jerry Yang, who co-founded Yahoo alongside David Filo in 1995, announced his resignation from the board of directors and all other company positions Tuesday, effective immediately. His resignation also applies to his board positions at Yahoo Japan and Alibaba, a Chinese conglomerate in which Yahoo owns a stake.

Jerry Yang served as CEO of Yahoo from June 2007 to January 2009. He stepped down after he refused a $47 billion buyout bid from Microsoft, which angered shareholders.  Carol Bartz was hired from Autodesk Inc., maker of the popular modeling program AutoCAD, to replace him. She too was fired, after she failed to revive the company.  Yahoo then hired current CEO Scott Thompson, former president of PayPal, earlier this month.

Thompson issued a statement to his employees wishing Yang well on Wednesday, saying Jerry will clearly be missed, but he has left an indelible imprint on this company he co-founded and built and an internet industry he helped pioneer.  The high standards he set for engineering excellence and a constant push for innovation will remain among the guideposts for our path forward.  Please join me in wishing him all the very best in this new phase of his life.  I assure you, we will make him proud.

Jerry Yang's departure means that neither of the company's co-founders are on the board any longer. Filo stepped down in 1996, though he is still an executive, with the title of Chief Yahoo.

Yang has repeatedly said that he refused to sell the company, a move that was widely panned by shareholders. His departure may signal that the company is ready to change it's mine. Fortune, however, reported that the board would not approve a takeover sale, though it's not clear if Yang's leaving changes that. Either way, investors see Yang's leaving as a positive move. After-hours trading saw Yahoo's stock up 5 percent on Tuesday, and it increased another 3% early Wednesday morning.