Most patterns of web site use follow what is widely known as long-tailed distribution. That is, a few items are overwhelmingly popular, and everything else gets relatively little attention. If you ranked the popularity of every web page in your site, you will typically see a long-tailed curve, in which the home page and a few other pages get lots of views and most others get much less traffic. This long-tailed distribution pattern in popularity is true for products in stores, books for sale at Amazon, songs to download on iTunes, or dvds for sale at Wal-Mart.
Although Wired magazine’s Chris Anderson popularized the concept of the long tail on the Internet, interface expert Jakob Nielsen first used Zipf curves (the formal mathematical term for long-tailed phenomena) to describe the distribution patterns seen in web site usage. Long-tailed usage patterns are fundamental to explaining why web search has become the most popular tool for finding information on the web, whether you are making a general Internet search or merely searching your company’s internal web site. Once users get past the home page and major subdivisions of a large site, they are unlikely to browse their way through all the links that may be required to find a specific page, even if every link is well organized, intuitively labeled, and working properly (fig. 5.8).