Continuity mistake: After the part where Merle and Daryl save the people on The Bridge, Merle gets agitated at Daryl and grabs him and rips his shirt. On the left side of Daryl's back, he has tattoos on his right side, but as he walks away he suddenly has the tattoos on his left side. (00:25:50)
Continuity mistake: In the scene where Merle is the in big box late 80's chevy with big 20-22 inch rims he is shown driving it in the barn yard drinking, playing music, and zombies following him. The shot changes a few times within the same scene with the big rims on, in one shot the car is shown with him driving it but the stock rims (15") are on the car, the paint of the car looks a little darker too. Then the shot changes again while he is still driving it and the big rims are on the chevy again. The shot that shows the stock rims is a pretty fast shot so it could be easy to miss.
Continuity mistake: When Rick, Carl, and Michonne are leaving King County (Rick's home), they must travel around a wreck involving two cars and an overturned RV. They drive along one side of the road. When the camera angle changes, they are on the opposite side of the road going the other way. (00:41:30)
When the Dead Come Knocking - S3-E7
Continuity mistake: The first shot of Maggie waiting for the Governor to enter shows her wearing a black tank top with her shoulders bare. After he cuts the duct tape around her wrists, the camera pans up and she now has black bra straps showing on her shoulders. (00:26:10)
Continuity mistake: When helping the foreign family to fight off the walkers, Daryl pulls the zombie back into the car and slams its head in the boot door, covering his hands in blood in the process. However, for the rest of the scenes in the episode and in shots directly afterwards, his hands appear totally clean without him doing anything to clean them. (00:22:00)
Continuity mistake: The previous episode ended with Rick and his group reaching Woodburry and it was dark. This episode starts with Tyreese and his group reaching the prison in the daylight, and being rescued by Carl and brought back to their cell block. If you look at the windows it is still light out, they have no electricity so it can't be exterior lighting, yet in the scene before and after this, Rick and his group are at the Woodburry at nighttime.
When the Dead Come Knocking - S3-E7
Continuity mistake: The Governor takes off his gun belt while interrogating Maggie, and a few shots later has it on again in the same scene.
Arrow on the Doorpost - S3-E13
Continuity mistake: In the final scene of the episode, Rick and Hershel are talking while looking out over the prison yard. Near the end of the conversation, Rick squarely faces Hershel and says "I'm hoping you could talk me out of it." The camera then changes to Hershel, and Rick is now immediately facing 90° to his left looking over the yard. When the camera changes back to Rick, he is now looking directly at Hershel.
Continuity mistake: When Andrea is attempting to retrieve the pliers on the floor she picks them up between her toes with the head facing up. In the next show the pliers can be seen with the head facing down when she grabs them with her hand.
Continuity mistake: When the Governor first attacks the prison, he is standing on the driver's side but in front of the truck. Next, Michonne aims at the truck and now the black guy who was always with Martinez is shot dead on the driver's side. Then after that, you see he's alive again on the passenger side right before the other truck comes crashing through the gates with all the walkers inside.
Suggested correction: The man you're taking about is Shumpert aka "Bowman." He's was not shot dead. He dove for cover and is still alive. In fact, he's in at least a half dozen more episodes, including in season 4.
Continuity mistake: When Rick, Michonne, and Carl go out on a run, in the first shot, Rick starts to roll the window down so he can shoot a walker. The next shot the window is up, and he rolls it down again. (00:02:00)
Continuity mistake: When Carl shoots the masked man who is found to be wearing body armor, Rick pulls up the armor to find the bruised ribs of a Caucasian male. When the assailant is unmasked however we see that the Caucasian male has magically transformed into an African American man. (00:11:20)