Keep in mind that if you read older texts, you might see "it's" where you'd expect "its". "It's" was originally used as both an abbreviation of "it is/has" and as the possessive pronoun of "it", but "its" came to replace it: "At first commonly written it's, a spelling retained by some to the beginning of the 19c." - Etymonline, which in turn took this quote from the Oxford dictionary.