It is spelt "hear hear" and is an exclamation of agreement, approval or support for a speech. Originated in British parliament in the 18th century as a contraction of "hear him, hear him".
Sorry, dazmac, but Spellmaster is right. Possessive nouns require apostrophes, possessive pronouns do not. "It" is a pronoun, and therefore "its" is the right possessive form, "it's" is a contraction of "it is". And now I've got a headache.
If you need any bedtime reading, wildwood, I can lend you a good grammar book. You should find page 311 especially interesting, it's all about its and it's. Sweet dreams! x