Continuity mistake: When Josey was in the general store picking up supplies with the Indian man and women, Josey was handed a picture of Slim Fixin. If you watch carefully, he walks out with the picture. When you see Josey after he has walked out of the general store, he does not have the picture in his hand.
Continuity mistake: In the scene where Josey and Jamie are about to ride off after killing the two bushwhackers (Abe and Lige), Josie spits tobacco on Abe's forehead. Look closely and you can see Abe's eyelids twitch. Also, notice where the tobacco lands. In the first shot, it's right next to Abe's receding hairline. But in the next shot, it's much closer to his eyebrows. His eyes are also open/closed between shots.
Continuity mistake: When Josey rides into Ten Bears' camp, Ten Bears bends down and puts some blood or war paint on his forehead. When he stands up the paint above one eyebrow is applied well, the other one is smeared. As Ten Bears is talking to Josey, both of them are well applied.