Take Back moves have now been added as another form of unrated game. This is a great learning tool for those who are new to the game, and for those who teach.
From Start New Game, under Show more advanced options. The Rated option offers a dropdown menu now containing three items:Rated game, Unrated game and Take back game.
The below link would help you..
http://support.chess.com/index.php?_m=knowledgebase&_a=printable&kbarticleid=22
when setting up a new onoine chess game, you get the choice of a rated game, unrated game or takeback game, what is a take back game?
thanks
craig