The Customer Sieve
http://www.uie.com/articles/customer_sieve/

User Interface Engineering
2002

Abstract:

We've learned that using a web site is a progressive process. Each user transitions from one stage to the next, as they work to accomplish their goal. The most pronounced transitions we've seen are on e-commerce sites. When we watch shoppers focusing on buying a product, we can clearly see each stage and when the transitions fail or succeed. By understanding the stages and how they work, we can learn a lot about building better sites.