Continuity mistake: Before the Roadhouse fire, Ash and Dean are talking on the phone. Ash looks at his watch, on his left hand, it says 8:10, and has a black dial/face. As Dean and Bobby go through the rubble, Dean identifies Ash by his watch. Still on his left hand, it is now upside down, evident by the crown of the watch (used to move the hands of the watch) which previously facing his hand, is now facing his elbow. Also, the dial/face of the watch is now silver instead of black. This is a different watch, and was inadvertently put on the burnt arm upside down.
Continuity mistake: In the scene where Dean is with Bobby at the burned down Roadhouse and Dean gets Andy's vision about where Sam is, the first time Dean scrunches his face in pain he puts his left hand to his head. The shot changes to a back view and you can tell his left hand is still at his head. But when the shot switches again Dean is bringing his right hand down from his head.