What's u'p wit'h th'e unnecessar'y apostroph'e? Like other possessive pronouns, (e.g.. ours, its, his, hers, theirs), the word "yours" does not include an apostrophe. Apostrophes are properly used to denote possessive nouns (e.g., Jim's, Mary's, the Martians').
The misplaced apostrophe has become an epidemic in our culture. There's literally a contagion of illiteracy occurring.