"It is not fair that people judge others by their mistakes."

Well, did you notice the mistake or do you think that this sentence is correct? The sentence has two major errors (which when spoken seems correct, but when written has a different meaning). Firstly, let's see what the correct sentence should be - "It isn't fair that people judge others by their mistakes". Just because 'fair' and 'their' are homophones, people can easily get confused with them. While speaking it is fine to some extent, but while writing, it goes unnoticed.