"I could care less" vs. "I couldn't care less"

http://dictionary.reference.com/browse/couldn%27t+care+less

http://www.dailywritingtips.com/could-care-less-versus-couldnt-care-less/

http://incompetech.com/gallimaufry/care_less.html

Idioms

13. couldn't care less, could not care less;

be completely unconcerned: I couldn't care less whether she goes to the party or not. Also, could care less.

somebody couldn't care less also somebody could care less

someone does not care at all Most fans couldn't care less about it.

World English Dictionary

care  (kɛə)
— vb  (foll by for ) (foll by for )
1.	( when  tr, may take a clause as object ) to be troubled or concerned; be affected emotionally: he is dying, and she doesn't care
2.	( intr; foll by  for or  about ) to have regard, affection, or consideration (for): he cares more for his hobby than his job
3.	to have a desire or taste (for): would you care for some tea?
4.	to provide physical needs, help, or comfort (for): the nurse cared for her patients
5.	( tr ) to agree or like (to do something): would you care to sit down, please?
6.	for all I care , I couldn't care less  I am completely indifferent