Continuity mistake: The tri-lens of the Martian camera becomes detached from its casing after Gene Barry pounds it to death. When he picks it up and puts it on a table, it rocks forward and comes to rest, facing down, on the table: the tri-lens is now firmly attached to its casing. (00:51:30)
Continuity mistake: When the Martian saucer crashes in the farmhouse while Dr. Forrester and Sylvia are eating, a long shot shows the Martian saucer crashing into the side of the house. Then it cuts to an inside shot with the wall (with a window) being smashed from outside in. Then it cuts to an outside shot again showing the meteor having collapsed the side of the house that was caving in, in the inside shot, however the meteor has crushed almost half the house - far more than what was happening in the inside shot. (00:44:30)
Character mistake: On several occasions, scientist (Clayton Forrester) refers to the impacting objects as "meteors". Any scientist knows (or should), that when a meteor impacts the the ground, it becomes a "meteorite".
Continuity mistake: A hatch opens-up to the martian saucer showing a very weak, limp martian arm moving slowly and lying against the door. Next scene shows a wide angle view of the people and the arm but the arm is now touching the belly of the craft. Another scene change has a close-up of the arm again resting on the hatch. (01:22:45 - 01:23:45)
Other mistake: When the Martians first land on earth, the ship is so hot, it starts fires in the surrounding area, and can't be approached for hours later. Yet later, when another ship crashes directly into the farmhouse, there are no fires, and the farmhouse certainly doesn't catch fire.