Collecting Feedback About Your Website's Search Interface
Webreference.com, Jakob Nielsen and Kara Pernice Coyne: "The ten high-selling sites complied with 40% of our usability guidelines for search whereas the ten less-selling sites only scored 27%. Even the best sites on the Web are far from having perfect search, but it is still remarkable to note the difference in search quality between sites that sell well and sites that sell poorly. Of course, rule #1 of ecommerce is: if the user cannot find the product, then the user cannot buy the product." (2000-11-05)
The link address is: http://webreference.com/new/searchinter.html