Over the weekend, I finally watched Lemony Snicket's A Series of Unfortunate Events on DVD. In Aunt Josephine's "suicide note," which was chock-full of clues (in the form of misspellings), there was one error that had nothing to do with anything:
my life will be at it's end
His, hers, yours, theirs, ours, its: no apostrophe for these possessive forms. It helps to automatically read it's as it is; this way, mistakes such as my life will be at it is end will never get through.