This invention improves upon existing pay-per-click arrangements by periodically generating a code associated end users. This code, preferably in the form of a serial number, is compared to the end user of the website, such that by observing a metric like the number of clicks for a given period of time, be it a short time or a longer period, such as a day or a week, the system can automatically determine if certain clicks are illegitimate. This allows the pay-per-click company to more fairly invoice the merchants, thereby preventing fraudulent over use.