This starts in the scene where Spiderman and the Green Goblin are fighting in the old building. When the Green Goblin is about to impail Spiderman and he jumps out of the way and it impails himself into the wall. Then, when Peter takes him back to his house he lays him down on the couch, but there is no blood or cuts in his shirt!?!
When the Goblin is killed by his glider, he is wearing his goblin suit, not regular clothes. More importantly though, when Peter (Spider-Man) lays him on the couch he is wrapped in a dark blanket. Any blood from his injuries would be contained within the blanket.