Revealing mistake: When the parted Red Sea comes together, if you look behind Pharaoh as his troops are being engulfed by the water, notice in the background that there are two boulders floating in the water, not being pushed, but floating lightly.
Revealing mistake: In the scene where Moses takes the first journey up Mt. Sinai for his very first view of the burning bush, the walking scene shot has Charlton Heston following the camera as the camera dolly's backwards towards the bush. As Heston and the camera movement comes to a halt, you can see two long tire tracks in the sand created by the dolly truck that housed the camera and cameraman.
Revealing mistake: All of the women in the film have 1950's-style haircuts.
Revealing mistake: When Rameses is casting Moses out into the desert, he stands in his chariot and delivers his speech about ruling over the scorpions. The pyramids behind him are 20th century photos, i.e. they look 4000 years old. In the time of Rameses, they would have been substantially newer - 1000-1500 years old.
Revealing mistake: When Pharoah's chariots descend into the parted Red Sea to pursue the Israelites, the path before them is neatly grooved with chariot wheel tracks and not trodden with the thousands of footprints and hoof prints of humans and animals that went before them.