This is how you do it: (a) Estabish what you spend on ads per visitor. (b) Establish what you earn per visitor coming from ads. (c) Only if (a) minus (b) is

This is how you do it: (a) Estabish what you spend on ads per visitor. (b) Establish what you earn per visitor coming from ads. (c) Only if (a) minus (b) is positive, continue running the ads. However, Facebook should have a look at this issue. It is the reasong why Google's AdWords is so successful, and most other self-service ad programs fail. AdWords is very good in filtering everything that does not represent a value for the costumer (the advertising web site).