Continuity mistake: When the gang of survivors goes to Andy's gun shop, one of them shoots a zombie and he proceeds to fall on his knees. The scene cuts to the gang and then to the charging zombies and the shot zombie falls again.
Factual error: When the survivors are first in the mall, you can see a store called Roots with a Canadian beaver logo. While the movie was filmed in Canada, it is supposed to take place in the USA where Roots has a different logo.
Revealing mistake: As Ana is driving away from her home, when we see her car driving from a shot high above, we see a car crashing in to a gas station making a huge explosion. However the trees a few feet away from the explosion don't move. The shockwave would have made them react at least a bit.
Continuity mistake: At the beginning of the movie, when Ana is escaping from her husband, she crashes into the bath and in the process pulls down the shower curtain and rail. The shot from above shows the curtain rail landing on top of her, but when the shot immediately switches to show to show a close up of her sitting in the bath, the rail appears to be propped up just behind her right shoulder.
Continuity mistake: At the birth of the zombie baby and the shoot-out, the pregnant girl gets shot through the left eye blowing her eye socket apart. Afterwards, the main blonde girl surveys the area and now the pregnant lady's left eye is undamaged.
Continuity mistake: When the group goes to rescue Nicole from Andy's shop it it is evening, when they return and must evacuate the mall it's night, but soon as they clear the horde in the parking lot it becomes early morning.
Continuity mistake: After Andy shoots the zombie that looks like Jay Leno, there are shots of the characters looking through binoculars. Tucker's and Steve's binoculars still have the lens caps on.
Continuity mistake: About 3/4 of the way through, CJ is on the roof of the gun shop and blows up a tank of propane to clear the zombies so everyone can escape. The truck that was blocking the door was their only way in and out of the shop. On their way into the gun shop you see two zombies follow them through the truck to the shop's entrance, but when he blasts the propane, somehow I guess they get cooked. My nitpick is that when CJ goes the same path as the others, there is a dead zombie blocking his exit through the truck's door. If the others already went out that same door they would have had to move that burned zombie to get through the truck.