About webpage navigation.

All web navigation must answer:

Where am I?
Where have I been?
Where can I go next
Where's the Home Page
Where's the Home Home Page

Navigation must be simple and consistent.
Common mistakes include different types of navigation on the same site, a link to the current page on the current page (home page link on home page), poorly worded links so the visitor doesn't know where he'll go if he clicks, no links back to the home page, confusing links to the home page, etc.
By Vincent Flanders