"A consistent style of presentation on each page allows users to locate navigation mechanisms more easily but also to skip navigation mechanisms more easily to find important content. [...] Predictability will increase the likelihood that people will find information at your site, or avoid it when they so desire.
Examples of structures that may appear at the same place between pages:
A navigation mechanism creates a set of paths a user may take through your site. Providing navigation bars, site maps, and search features all increase the likelihood that a user will reach the information they seek at your site. If your site is highly visual in nature, the structure might be harder to navigate if the user can't form a mental map of where they are going or where they have been. To help them, content developers should describe any navigation mechanisms. It is crucial that the descriptions and site guides be accessible since people who are lost at your site will rely heavily on them." 
Copyright © 2001-2003 by Rainer Hillebrand and Thomas Wierlemann