Sitemaps and Site Indexes: What They Are and Why You Should Have Them
http://www.boxesandarrows.com/archives/sitemaps_and_site_indexes_what_they_are_and_why_you_should_have_them.php

Fox, Chiara
Boxes and Arrows
2003

Abstract:

Sitemaps and site indexes are forms of supplemental navigation. They give users a way to navigate a site without having to use the global navigation. By providing a way to visualize and understand the layout and structure of the site, a sitemap can help a lost or confused user find her way.