I just played a game of Go at the KGS server using CGoban 3 against a beginner. He mistakenly marked a group of mine as dead that was very much alive. I tried clicking on it, but the dead or alive status of the group did not change.
How can I unmark a group as dead? How is it handled if the players disagree about the status of a group of stones?
According to this amazing FAQ page - "Revive the stones with shift-click on one of the marked stones. If your opponent insists in marking living stones as dead, ask for a referee in one of the chat rooms: nearly every stronger player is able to settle a dispute of this kind."