Measuring the number of people that have seen the Web site can give an estimate of awareness, but no method is able to judge Web site recall or if the person has put the Web site's product into their consideration set. Knowing who uses a Web site is only the first step in determining if the site, as a vehicle for advertising, is effective. The problems mentioned above need to be solved before companies will have an accurate representation of the overall effectiveness of their web sites. Proxy servers allow web documents to be stored so than when someone requests a web document the document is stored in the server's memory. This decreases the number of clients that the server registers, and could cause problems in the heuristics that are developed for that site.
Cookies are one way that servers are able to measure their audience on-site.
The cookie can track how much time is spent within a site and can follow the user to subsequent sites. Web users however, are becoming aware of cookies. The software keeps the cookie from attaching so no information can be collected about that user. This software prevents the server from collecting a representative sample of their web audience. Recent years have seen growing expenditures spent on on-line advertising.