Improper use of the apostrophe for plurals bugs the hell out of me. Except in narrow circumstances, one places an apostrophe before an s to denote possession. If one is discussing more than one of something, the apostrophe goes after the s. One does not place an apostrophe before the s to simply denote plurals.
No apostrophe is used in the following possessive pronouns and adjectives: yours, his, hers, ours, its, theirs, and whose. (Many people wrongly use it’s for the possessive of it, but authorities are unanimous that it’s can only be a contraction of it is or it has.) Except for one’s, no possessive determiner has an apostrophe. A number of them, like its, are homophonous with pronoun-auxiliary contractions. As was previously noted, the pronoun its is very commonly misspelled; not only is there the homophone it’s (it is or it has), but ‘s is a genitive clitic.
For cryin’ out loud people, get it right.