Rep Power: 233

Hi i have a 2003 honda civic ex sedan and i stopped at the store to get gas the other night and when i drove off my air bag light comes on and i dunno what could have set it off but would the backseat belt stuff set it off or would it just be the front any ideas are welcome cause i really dont want to pay the 70 dollars to have honda hook it up to a computer but more than likely will need them to do it but dont wanna on the title obviously i ment air bag light lol i cant figure out how to change it