Why is it bad luck 2 spill salt?

Salt was once used as part of the salary of Roman soldiers.

To spill salt is to spill (loose) money, which most of us see as bad luck.

The antidote to spilling salt, is to throw a bit of it over your left shoulder.

The devil is said to sit behind your left shoulder waiting to see you do something that will allow him to harm you.

By throwing the salt over your left shoulder you will be throwing it into the devil's eye and he can't see that you should have bad luck.