Lies

Is it ever ok to lie?  This question has crossed my mind as I parent my children.  Is it ok to tell them there is no candy in the house when if they were a foot taller they would see it in the pantry?  Are white lies really any different than full blown lies?  Is it a "character flaw" as my husband describes?  And more important if you get caught in a lie do you lie again to get out of it?  And if so, when does that end?