AutoTrader.com and Kel­ley Blue Book’s Kbb.com will work togeth­er to expand their online clas­si­fieds. This move gives deal­ers and con­sumers sell­ing vehi­cles access to a greater num­ber of prospec­tive buy­ers: an esti­mat­ed 26M unique poten­tial buy­ers between the two sites.