Navigation

Three fundamental questions of navigation: Where am I? Where have I been? Where can I go?
Success of navigation text links depends on predictability of where the link leads and differentiation of one link from others.
... Differentiated links improve usability.
... Check the inc.com research page.
Use descriptive text for a link; avoid using "click here" as the text for a link - there's no information content.
... Example of poor design and better design.
"Child" links and information in "content area"; navigation to other topics placed in margins; upward navigation or "breadcrumbs trail" shows logical hierarchical path to this page.
... Page layout concept.
Links that are graphics depend on waiting for image download; text links appear faster.
Tabs are often effective for navigation - support a clear physical metaphor.
... drugstore.com and MIT Sloan are good examples.
Page layout can support a clear navigation model for the site.
... Tony Braun Information Design is a good example.

References:
Spool et al., Web site usability: A designer's guide, 1999.
Nielsen, Designing web usability, 2000.