Why are the brakes still squeaking?

any time you change the disc brakes,either turn the rotors or buy new ones if they are not in spec.also if you buy new rotors,turn them too.warped from sitting on shelf.don't know which ones you need,2 diff.ones listed. www.napa.com or www.autozone.com or www.advance.com or www.oreillyautoparts.com