It could be a bad master cylinder... the light also comes on when there is a pressure difference between the primary and secondary lines to give you a warning.

 

ok thanks i havnt got teh chance to get it filled up due to weather and a garage thats filled up right now...ive had my car in for safety chekc recently..but i dont trust that too much because since that less than a month ago ive had to go get coolant for teh engine and now this apparently....and tehy told my mom she needed new tires on her stang when hers are just fine...and of course it has her going crazy wanting to get new ones