It depends on what state you live in. For example Texas is a "Right to Work" state, which means that an employer can fire you for any (non-discriminatory) reason. It also means you can quit for any reason.
If you were looking for a job on company time, that could be grounds for termination.
If you are an "At Will" employee or live in a "Right to Work" state he can fire you you for any reason, but if the termination was not justified, you can file for unemployment.
