Airbag Light On
It's on, find out why and what it means
I Hit A Pot Hole
It probably knocked a connector and caused a fault.
The fault will probably be "high impedance in air bag system" or something like that.
There is really nothing to fix, just get the light turned off and don't hit any more potholes.
I Moved The Seats
You have seat side air bags then.
These are a weak point in the car.
I would personally swap the connectors for something better.
I Crashed
Even if the airbag didn't deploy, in a half decent crash the seat belt pretensioners will fire.
This locks the seat belts and turns on the airbag light. You will need new seat belts.
I Was Messing Around In The Boot
You may have knocked the side boot trim and affected the connections to the seat belts.
I Can't Get The Light To Go Out
No amount of fixing and disconnecting batteries will turn the light off.
You need to visit smart or a smart specialist to have them erase the error code.