But, we reserve the right to change your payout rate. It can be moved either up or down. But, we will always give you advance warning before changing your rate of pay, and will never do it retroactively.
As the quality of 404 traffic varies so widely, we must be able to change the rate of pay. The majority of webmasters will be paid $4/1000, as we've found that this is the average quality.
Note that we only pay for traffic that is looking for a webpage, and not for images. That is, you will not be paid for any broken images on your page that generate a 404-File Not Found error.