Continuity mistake: At the start when Azeem is tied up in the prison, at one point when he asks the Christian to free him, his hands are tied at the wrists, then apart tied to the wall, and then back to his wrist all in three quick takes. (00:05:15)
Continuity mistake: When Robin reaches his homeland, after he kisses the ground, he rolls over in the water. His coat is covering him, then in the next scene, it isn't, then it is, then it isn't. (00:12:15)
Continuity mistake: When Robin and Azeem are escaping on horseback from the sheriff's men at Marian's castle, crossbows are being fired at them from the left side and one hits Robin's horse. When Robin pulls the crossbow bolt from his horse a minute later he pulls it from the horse's right side. (00:35:05 - 00:36:00)
Continuity mistake: When Robin is testing the river before they cross, the rope that trips him is seen below the water looking bright yellow. But once out of the water, it looks brown with moss on it. (00:39:00)
Continuity mistake: Just before the 'one true weapon' speech, one of the villagers shows Robin what the soldiers did to his son, Will walks toward Robin and pulls his dagger from its scabbard, after Azeem says 'if it's fame you seek.' the camera goes back to Will and he is no longer carrying it. In the behind shots, it can be seen back inside its scabbard. (00:55:00)
Continuity mistake: When the soldiers are taking anything valuable out of a village church, when they put up a wanted poster outside, Robin shoots an arrow into the poster and then Little John rips it of the wall and shows it to the men. When someone says, "Give it back" the soldiers drop what they are holding, and the poster is still on the wall with the arrow through it. (01:00:00)
Continuity mistake: When Robin and his men steal the cart of brew and Friar Tuck, the Friar's trousers (that he is wearing under his brown robe) change colour repeatedly between shots. When he is singing, and when he is trying to sit up after the men have opened the chest of money, the are flesh coloured (cream). But when he has been hit on the head by the branch and falls from the cart, they are brown. (01:05:40 - 01:06:45)
Continuity mistake: In the big fight scene in the forest Robin is not wearing his necklace. But when he goes to help save Fanny before he swings across the necklace suddenly is around his neck. (01:39:40 - 01:40:25)
Continuity mistake: During the hanging scene, after Wolf attacks Will, when Will is brought to the front of the crowd the manner in which the two guards restrain him changes repeatedly between shots. (01:54:05)
Continuity mistake: During the hanging scene, when Bull cuts the rope to close the gate, he cuts it and runs so he doesn't get squashed by it, but in the zoomed out shot, he is suddenly on the ground and rolling away. (01:57:20)
Continuity mistake: When Robin is burying his father, he cuts his hand saying, "I swear it by my own blood" and that he will avenge his fathers murder. We see the blood dripping over his fingers. Suddenly the camera shot changes and Robin's hand has no blood seeping between the fingers.
Continuity mistake: When Robin reaches the cliffs after escaping from prison, he jumps out of the boat and starts kissing the ground. He then reaches out with his right hand for help up, but when the camera switches, he's being lifted by his left.
Continuity mistake: When Robin heroically swings across to Fanny and the child in the Sherwood Forest battle scene: He swings straight across, with the rope's focal point fixed between himself and Fanny. Then he gives the rope to Fanny to swing across to John. This time the focal point is between her and John. Someone somehow managed to "move" the rope in order to move the plot along. That was jolly nice of them wasn't it?
Continuity mistake: When Azeem first blows something up, the Friar is next to him and Will, Robin, John and Bull are seen behind them around the model of the castle. However when it goes to the next shot there's only Will and Robin around the model. John and Bull walk in a few seconds later.
Continuity mistake: When Robin goes to the Church, the camera pans down from an enormously high vaulted ceiling in a vast cathedral. A few moments later, Robin and the Sheriff come running out of the Church and it's a small little stone shack.
Continuity mistake: At the execution scene where Will Scarlet is about to be beheaded, Robin picks up a burning arrow to shoot the executioner. When the arrow is first picked up from a dead body, the flame is half-way up the arrow, but when Robin fires it, the flame is (conveniently) at the arrow's tip.
Continuity mistake: When Robin first goes to visit Marian, he enters the house with a roll on his back (over the shoulder). It's there when he enters and the maid tells him to 'stand right here'. A moment later "Marian" appears, and the roll is gone, it's not on his back, or even in a wide shot showing he took it off. It never appears again.
Continuity mistake: Throughout most of the film, Robin wears brown boots with metal studs around the calf. When he is fighting the Sheriff of Nottingham at the end, he is suddenly wearing greyish boots, with cross-garters. Since you see his brown boots just before he enters the castle - when he kneels down near the dung they're especially visible - it is rather ludicrous that he would suddenly change them, given that he is rushing around trying to save the other outlaws, and then Marian.
Continuity mistake: When Marian and Duncan leave the camp by boat, Marian's lady-in-waiting, Sarah, is nowhere to be seen. Surely she should have left with Marian, as she is with Marian later in the chapel.
Continuity mistake: This mistake makes sense only if you've seen the extended edition. In a deleted scene, it is understood that the sheriff cuts out his scribe's tongue. In a later deleted scene, the scribe has to write messages on a chalkboard to communicate. Later still, at the end when Robin and company invade the castle, Robin asks the same scribe where the sheriff is and he verbally tells him, "Up the stairs," or something similar. Maybe he could speak a little, but he wouldn't have been able to pronounce the letter 'T'.
Answer: The white robes, reference to "the old ways", and pentagram across the map when the Sheriff meets the Barons suggests per-Christian Druidism; the upside down crucifix certainly implies Devil-worship. These two spiritual paths are, by nature, mutually exclusive. In short, a fictional pseudo-witchcraft invented for the film, yes.