When Macbeth placed the dagger on the young warrior's chest, he places the dead man's hand on top of the blade. In the next shot, the dead man's hand is rested on his chest - below the knife.
When Macbeth and Lady Macbeth are alone, his crown appears to rotate between shots.
As Macbeth walks towards the witches for the first time in a wide shot, the sheer socks protecting his supposedly bare feet are clearly visible.
Some sets (particularly the cathedral) show examples of gothic architecture, an art style that started in the 12th century. However, Macbeth ruled in the middle of the 11th century, when gothic architecture didn't exist.