When I am proofreading, I often find that it’s is used when its would be correct. I think that this occurs because the writer is thinking about apostrophes as a way to show possession. However, its is a possessive pronoun. It doesn’t need an apostrophe because it is already the possessive form of it.
Its means ‘belonging to it’.
It’s means ‘it is’ or ‘it has’.
The following are also possessives and don’t require an apostrophe: hers, his, mine, yours, theirs and ours.