Documenting bad grammar

Lee and I share a pet peeve relating to grammar, and he has chosen to begin documenting finds in meatspace.
One reason I don’t slog through comments on most blogs is because the respondents apparently didn’t learn anything in third grade, or since. “It’s” means “it is,” and “Its” denotes the possessive case. “There” denotes a place, while “Their” denotes a plural possessive. Those are the two major mistakes I see, which irk me to no end.