The airbag light shoud also set a code. The code can be obtained by a service tech. Or you can purchase an inexpensive code reader (OBD II) from an automotive store (Pep boys, Autozone, etc) The light could be caused by a fault in the airbag circuitry, crash sensors, the airbags themselves, or the seat belt circuitry or latches. The code will set you in the right direction.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.