Its and It's ...

How many times have you seen sentences using "its" where it be should "It's" and vice versa?

Well it is a very common error, however it is a very serious one too.

Here's the explanation:

• Its
  pronoun
  
  the possessive form of it (used as an attributive adjective): The book has lost its jacket. I'm sorry about its being so late.

• It's
  contraction of
  It is or It has.
  

Confusables note

A very common mistake is to write its (the possessive form of it ) when it's (the short form of it is or it has ) is required: It's [it is] unclear what he meant. It's [it has] been wonderful seeing you again. But do not use it's for it has when has is the main verb: It has a strong flavor; use it sparingly cannot be written as It's a strong flavor… An equally common mistake is to use it's for the possessive, probably because ordinary possessives of nouns are formed with an apostrophe: the dog's coat; Mary's cell phone. But the possessive its is a pronoun, not a noun, and, like other possessive pronouns ( his, hers, yours, and theirs ), is written without that particular bit of punctuation: I have to fix my bike. Its front wheel came off

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