A startup usually comes with the connotation that you will scale it to some sort of ideal (whether that be revenue, the people or businesses you have an impact on, etc.). A site that pulls in a decent income via advertising is really just a lifestyle business with little chance of scaling. Now if you made a network of these sites or found some other scalable product coming from this site.. then you'd have a startup, no? No one says you have to build a startup though.