Continuity mistake: When Tony is working on the laptop in the van, the IP address shows as 934.554.32.3. Not only is that an invalid address, but when he enters Rhodes' credentials, the IP changes to 93.455.43.232 (also invalid). (01:05:45)
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. (01:12:50 - 01:14:10)
Factual error: When Maya is trying to get Killian to let Tony go, she holds a dose of Extremis to her neck and says "1200 cc's - A dose half this size, I'm dead." 1200 cc's is 1.2 litres, or over 40 oz/2 pints. What she's holding is barely the size of a cell phone, nowhere near that volume. (01:22:50)
Continuity mistake: When the suit starts to arrive at the bad guy's house in bits, Tony Stark is walking down a long hallway. Scene cuts to outside and his facemask arrives, but the building he is in front of isn't big enough for the hallway we just saw. (01:28:15)
Continuity mistake: When Tony Stark and Col. Rhodes confront the Mandarin in his chair the hammer for the Beretta is forward after Rhodes loaded a new magazine. The hammer is shown in the back position in a subsequent shot. It happens twice during this scene. (01:30:05)
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. (01:30:10)
Continuity mistake: When Tony and Rhodes leave the Mandarin's mansion, Tony has blood on his left eye and cheek, which changes to the other eye between shots, then changes again at the boat. (01:30:25)
Continuity mistake: Just before Iron Patriot boards Air Force One he is shown with red illuminated eyes. Later when he enters the office onboard before he takes the president his eye colour changes to blue. (01:31:51 - 01:32:50)
Factual error: When the Iron Patriot armor is shot at on Air Force One, the bullets ricochet and smash a window. The windows on Air Force One are bulletproof. (01:32:55)
Revealing mistake: One of the Air Force One survivors is shown floating awkwardly on his stomach with his legs in the air. This was due to the floatation device used by the actor, because no unaided human would be able to be so buoyant in a pose like that. (01:37:00)
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. (01:41:15)
Continuity mistake: When Tony leaves the bar, his hands are cuffed behind his back. When he is shot at in the next scene after jumping through the window, his hands are somehow cuffed in the front of his body. (01:54:50)
Factual error: At the end Tony drives an Audi R-8 e-tron, which is an electric car, and while it has a sound system to produce an artificial engine noise, it doesn't sound like what is heard. (01:59:20)
Other mistake: When Tony's house is destroyed by the Mandarin, watch closely when Pepper is blown through the air, just before Tony attaches his suit to her - she's very obviously wearing high-heeled shoes that would make it impossible for her feet/ankles to fit correctly into the suit without them being crunched up by the suit's boots. But later on, when she gets out, if you listen, you can hear the "clicking" of her unbroken heels as she runs around.
Continuity mistake: When Tony is talking with Rhodes at the bar, his chest is not glowing.
Revealing mistake: When Tony and Rhodes are on the oil tanker bunkered behind an obstacle, Tony realises his gun is empty and asks Rhodes for a new magazine. When Tony ejects the magazine you can see that it is actually an airsoft gun magazine; thus exposing that it is actually a prop gun.
Continuity mistake: Colonel Rhodes holds his pistol to the face of the Mandarin in a close up shot, then lowers it. The next instant shot later of Rhodes show him still holding the pistol to the Mandarin's face.
Character mistake: Killian tell Pepper the "primary somatosensory cortex" is the pain center. However, this is a gross exaggeration someone of his knowledge would not say. One, the area handles all tactile (touch) receptions. And two, other areas of the brain handle pain, so there's not a "pain center." However, the area that lights up is also wrong, because only the right side would be stimulated since it was his left arm that was touched.
Revealing mistake: When Tony is knocked violently forwards during the test of the Mark 42 armour, he somehow arrests his fall mid-air just before propulsors in his hands actually fire, because the effects weren't perfectly synced with the wirework.
Continuity mistake: The wound on Maya's forehead changes color, angle and position through the film.
Chosen answer: The Battle of New York was never specified to take place in 2012, we just know that the film came out then. Based on the newspaper we can assume that the battle was in June 2013, rather than some time in 2012 as many would have previously assumed.