Continuity mistake: In the scene when Diana is invited to tea and then Anne follows her home after Diana has become drunk, Anne's tights change colors, from black to white several times.
Other mistake: When Matthew and Anne first arrive at Green Gables, the person playing Matthew is not Richard Farnsworth, but a stunt double whose hair is quite obviously shorter than Mr. Farnsworth's. The stand-in's face is clearly seen as he walks around the carriage (Anne is in the foreground, close up). The stand-in is still taking Mr. Farnsworth's place as he walks Anne to the front door. The shorter hair is obvious in this view of his back.
Continuity mistake: When Mr. Philips has Anne write lines on the board, in the first shot the 's' in Shirley is cursive, and in the second shot, it's printed.