Continuity mistake: After Tony gets the armor back at the Mandarin's hideout and meets up with Rhodes, they go by boat to the harbor. On the way Tony calls the Vice President - during this scene the VP's phone changes, note the camera on the back of the phone is visible, but in another shot right after, it is a completely flat back panel.
Continuity mistake: Tony is in the bedroom with Maya Hansen, Happy is seen closing the sliding door. With the door just inches from being fully closed, a quick cut to Tony and Maya kissing, then back to Happy, and the door is almost fully open, with Happy in the process of closing it again just as the plant explodes.
Continuity mistake: When the Mark 42 is "done" assembling for the first time, in Tony's workshop, a digital model of the suit appears in the lower right corner of the screen. In this render, the suit is complete, but a moment later there is still one piece missing, which hits Tony so hard the entire suit falls apart.
Continuity mistake: When Tony is creating his weapons, one shot shows the electric glove he is wearing to be designed for his left hand. Later on, when he is in the Mandarin's mansion, he attacks one of the guards with the electric glove, only now the glove is on his right hand.
Continuity mistake: When Tony and Pepper are attacked by 3 missile-wielding helicopters, Tony, dressed in his metallic suit, has blood on his nose and cheeks. Problem is: The blood increases on his face, which is normal as it is still bleeding, but then it lessens. Then it gets worse again.
Continuity mistake: When Tony is attacked by helicopters in his Malibu mansion, his right hand has a black wrap around it. After he gets buried by rubble underwater in the suit, his right armored hand detaches and grabs his bare right hand to pull Tony out from the rubble. Tony's bare hand no longer has a black wrap.
Continuity mistake: When Tony and Rhodey first get noticed as they search the oil platform, one of the Extremis soldiers starts shooting at them. They dodge the bullets and hide. Tony then says "You see that? Nailed it" and he is shown to be looking at Rhodey. Next shot, he's suddenly looking downwards.
Continuity mistake: As Maya is showing Tony her research, in the shot where Tony says "Essentially, you're hacking into that of the genetic operating system...", Tony is shown to be looking at Maya. Then as he finishes off the sentence with "of a living organism" in the following shot, Tony is suddenly looking at the computer.
Continuity mistake: When Tony tells Killian to go to the roof, he leaves the lift. In this shot, there is a strand of Killian's hair layed over his face and nose in a straight line. In the next shot as he says "I'll see you up there", the bottom of the strand is suddenly curved over to the left side of his face.
Continuity mistake: After Tony hangs up on Happy using Face-Time, the scene cuts to Pepper and Killian having a conversation. As Pepper says "As in, enhanced soldiers, private armies, and Tony is...", she is cut off by Killian. When Killian starts speaking, he shifts his head to the left and starts looking downwards. In the next shot, he is suddenly looking straight back up at Pepper.
Continuity mistake: In 1999, when everyone exits the lift, Tony and Killian stay inside the lift. As everyone leaves, Tony places his hand on the door frame. In the following close-ups of Tony and Killian, Tony's arm never shows any signs of moving his hand, but as he leaves the lift, his hand is no longer on the door frame.