All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
The nature of this dealing may have one of the following two situations:
First, it could be a rental contract i.e. you rent out some space on their site to use it for the advertisement of your site. If it is the case then it is an invalid rental contract since it is a condition for the validity of a rental contract that the fees are known and there is no ambiguity regarding the contract. This condition can not be fulfilled here because the company might make a lot of profit if the visitors are many, while on the other hand they might not earn any thing if there are no visitors. This uncertainty invalidates the contract. In an invalid rental contract the contracted party deserves conventional wages.
Second, it could be brokerage i.e. you make an agreement with Google that they will bring visitors for your site on the condition that you will pay a fixed amount for each visitor as a commission; this is allowed since it is a kind of hiring contract which is allowed if the wages are known.
Finally, all the above details apply if the content of your blogger is lawful; otherwise, it is not allowed.
Allaah Knows best.