Continuity mistake: While breaking down the bathroom door with the axe, Jack repeatedly strikes and damages the right hand panel, but as he turns away from the door (when he hears the snow-cat) both left and right panels have been damaged.
Continuity mistake: When the windows on Nick's truck are smashed, Elizabeth has protective gloves on when she covers her face from the glass, they are then gone when the truck comes to a halt.
Continuity mistake: After Brenda hears a noise, she puts her book down next to the candle, and walks to the door. When she gets to the door, the book is now by the opposite side of the candle. (00:52:50)
Continuity mistake: The amount of blood on Kate's face decreases between the time she is attacked and discovered. The pattern changes from shot to shot as well. (00:34:15)
Continuity mistake: When the lady anthropologist gets out her teacher's car - you can see in the background the traffic lights changing from green, to amber, to red. When it cuts to another view of her - the traffic lights are on green.
Continuity mistake: Kim is at the kitchen table with her brother Alex. Kim has a necklace on. Kim asks Alex about having a date for the prom and all that is around her neck is a gold chain. The shot then cuts to Alex and then back to Kim and now there is a gold star hanging from her necklace.
Continuity mistake: At the end, the buried biker digs himself out of his grave and shuffles to the smokehouse. When he attacks Farmer Vincent, all the soil and mud stains have vanished from his clothing. Guess he must have stopped off at Zombies-R-Us for some fresh new duds. (01:30:00)
Continuity mistake: Kenny must be fast. He's disguised as the female assistant at one point then minutes later he's disguised in the Groucho Marx costume.
Suggested correction: It's not a full costume. Kenny steals the mask and what looks like a small waistcoat (leaving even the hat). It's not implausible that Kenny made a quick change (probably after killing Ed) to formal wear (which isn't what Ed was wearing). After Ed's murder, Kenny-as-Ed appears briefly only from the waist up (showing only the stolen mask and waistcoat), and then doesn't appear again for quite a few minutes, more than enough time to change to the formal wear.
Continuity mistake: When John finds the diary in the hidden attic room the date on the front reads "January 1909", however later on when Claire reads it she says "January 4th 1909." (00:33:55 - 00:36:38)
Continuity mistake: The amount of blood in the shower varies from shot to shot. One moment, it's ankle deep, then the drain is visible, then ankle deep again.
Continuity mistake: At the beginning during the house gathering, the toilet seat is up while Arthur is gathering ice from a bag that is in the bathtub. We cut to a shot of Emily and then back to Arthur, where the toilet seat is down. (00:06:40)
Continuity mistake: The woman next to Slade when he's at the BBQ at the party holds her glass up, down, up in different shots. (01:14:40)