Factual error: When the Indians are running from the cavalry they cross over a set of tire tracks. They are too far from where Marty started so cannot be his, and the lines can't be wagon tracks because the lines are too wide and the width is uniform. (00:19:30)
Continuity mistake: While Marty is fighting Tannen the sun changes between shots.
Character mistake: At the ravine, upon learning that the bridge doesn't exist yet, Marty states to Doc "We can't wait a year and a half for this to be built". If you carefully look at the sign, it says the bridge is opening Summer 1886. That's under a year away, not a year and a half from Sept. 1885.
Continuity mistake: Watch as Seamus hands Marty the baby, there is a definite "jump" and Marty is facing in almost completely the wrong direction, looking for a clue from the set's crew as to where he should be looking to catch the baby from... (00:24:20)
Continuity mistake: In the end scene where Doc's train comes back to 1985, Marty and Jennifer are literally blown away by the re-emergence of the train. While they are flying in mid-air, the front of the train is passing them by and gets just about to the cab (where the ELB is). However in the next cut, Marty and Jennifer are on the ground watching as the train just starts passing them again, and the train comes to rest at a point before the previous "blown away" cut scene.
Chosen answer: Yes. A "googol" is the number 10 raised to the 100th power, or a 1 followed by 100 zeroes. A "googolplex" is an even larger number - 10 raised to the power of a "googol", or represented as 1 followed by a "googol" zeroes.
BGraz