The incorrect apostrophe in "it's"really annoys me, Perplexed. I know it shouldn't, and I should get a life, etc, etc. But it's really very simple. It's a rule with no exceptions. "It's" is ALWAYS an abbreviation, for either "it is" or "it has" (as in "it's been raining today"). Otherwise it is what is called a possessive adjective (or just conceivably a possessive pronoun) and has no apostrophe. Other possessive pronouns which do not require an apostrophe ar "hers", "yours", "ours", and "theirs". Another common mistake is "who's" for "whose". Since it requires an extra keystroke to put the apostrophe in, I cannot believe that it is a mere "typo" when it appears.