How much money can a website earn by advertising?

It depends on the amount of visitors, the type of site and advertising. Generally, the more visitors, the more potential advertisers and the more money you can charge for advertising. However, some sites are just not ideal for advertising because of the content or target audience. Whether you sell advertising directly or whether you go through a service such as PPP or google's Adsense make a difference, too, because they all have different operations. some websites make very little, just a few dollars a month or maybe enough to cover paying for the website where others make enough revenue in advertising to live off of it some websites & programs are scams.