Visible crew/equipment: When the Sheriff of Rottingham is hanging upside-down under his horse and talking to Robin, look at the legs of the "horse": one of them has the visible joint of the knee (obvious as the light hits it when it bends) and the other doesn't look like it's actually touching the ground at all, though from the angle it looks as though the leg was intended to be seen as weight-bearing.
Visible crew/equipment: As Marion jumps off the balcony onto her horse, when she lands, you can see a pair of hands holding the horse's bridle as it moves its head. There's nobody there when they show a wider camera shot of her on the horse. (Seen in widescreen.) (01:04:10)
Answer: Gibberish.
It means literally "I will send you to hell".