Continuity mistake: When Dr. Meade announces General Lee's victory (and later Rhett Butler as a special guest) at the "Monster Bazaar", he speaks to a backdrop showing the audience with a soldier with a drum standing left to him. Behind him, a couple in black is dancing. When he moves, Rhett and Scarlett are revealed, going to the rear of the dance floor. Clearly they haven't met at that point, as they are introduced by Melanie moments later.
Continuity mistake: When the curtain gets stuck to Ballantine's pants, at first it's stuck on his side, then in the next shot it's stuck in the middle of his back.