Continuity mistake: When Debbie is killed in the hammock, in all shots of her, the quilt covering the hammock net has patterns sown on it, such as flowers. However, in the closeup of Debbie as the knife comes through her chest, the quilt covering the hammock is the same one as before, however you can now see it is suddenly the other side of the quilt.
Revealing mistake: When the snake leaps out of the cage, you can see a dodgy looking fake snake attached to a wire spring.
Plot hole: Jason somehow manages to get the two halves of Andy's dead body on the wooden ceiling rafter, with no blood dripping onto the hammock and staining it, or getting none onto the floor. Debbie then gets into the hammock, and about a minute later, blood starts dripping - for no apparent reason. Why?
Continuity mistake: When Chris and Rick get stuck in the woods, Rick puts a coat on Chris. In a wide shot Chris pulls the sleeves of the coat up and then starts adjusting the shoulders of the coat. It cuts to a closeup and she is now rolling the sleeve up again, and then adjusts the shoulders again too.
Revealing mistake: During the opening sequence involving Harold and the clothesline, there is a foreign object on the lens of the camera - noticeable in the bottom left corner in several shots.