Continuity mistake: After Salt is arrested at the V.P.'s funeral, the police vehicles drive up a ramp directly behind the building with the Silvercup studios sign on the roof, yet when she is attempting to escape and rams the SUV she is in into the back of the escort patrol car in front of her, you can see they are now in front of the Silvercup studios building which is now a couple of blocks away in the background.
Plot hole: In the end, all they have to do is ask the President, when he's conscious (Liev didn't kill him; he just knocked him unconscious), who killed everyone in the control room and nearly killed him. He would know who the traitor is and it's not Salt - when they look back at the facts, they'll see how Salt only killed when she absolutely had to, and how she saved lives and stopped a 3rd world war.
Continuity mistake: Salt is in the Russian boat approaching the radioman. She throws some grenades down the stairs and some around, and explosions occur with fire and bits and pieces flying everywhere. Then she goes for a walk to kill some more guys and when she comes back to the same place it all looks nice and clean as before, no dust, no mess at all.
Revealing mistake: During the scene where Salt spreads her belongings on the bed of her hotel room after the opening chase, you can see in the close-up shot that the primers of the bullets are missing. This means that the bullets are lacking the necessary components (both the primer and the gunpowder) to actually be fired.
Other mistake: When Salt is arrested and in the back seat of a police car, somehow she takes control and causes a lot of smashed up cars, and hits about ten large yellow bins. The problem is: Those bins are there because they have water in them, to lessen the impact of crashes, but there was no water to be seen.