Yahoo! chief executive Carol Bartz defended her turnaround efforts at the Internet pioneer Thursday and won the endorsement of the company\'s chairman and shareholders. But Yahoo!\'s annual gathering of shareholders ended on a dark note when an investor challenged Bartz to explain the company\'s languishing stock price and posts by bloggers contending that a hunt was on for her replacement. The investor, who claimed to be an advisor to stockholders with big stakes in Yahoo!, urged the board to be open to selling or breaking up the company. \"Thanks for your opinion, the blogger\'s opinion, and the rumors,\" Bartz replied, not addressing any of the points raised. \"That was certainly a downer.\" Bartz assured shareholders that she was leading a focused effort to transform Yahoo! into \"a premier digital media company\" serving up online offerings tailored to the tastes of its 680 million users worldwide. Bartz and board chairman Roy Bostock were supported by about 80 percent of the voting shareholders, while the remaining eight board members saw backing closer to 90 percent. A shareholder-crafted proposal calling on the Sunnyvale, California-company not to do business with China \"and other repressive regimes\" failed to get enough votes to pass. The proposal was opposed by the board.