Structure
People are accustomed to hierarchical representations of information. Nearly everything we talk about can be divided into categories, then further divided into sub-categories. Always start with broad categories, then move to specific ones. This applies whether you are finding a street address (start with country, then province or state, then city, . . .), classifying species of animals, organizing books on a library shelf, or determining genres of music.
Effective websites build on this hierarchical view of the world. On this site, the navigation bar at the top of each page displays the major categories. The sub-menu on each page displays links to all of the pages within a major category. And the site map for this site lays out the entire hierarchy.
Every page is accessible from one of the menus. Where appropriate, some pages are also accessible as links from other pages, but visitors should never have to rely on finding the link to a page within a paragraph of text. These links are provided as a convenience to visitors, while the primary navigation is via the menus.
Consistency is very important. On this site, every page follows exactly the same layout. The same types of navigation tools are always available in the same locations. Visitors do not get lost simply because they move to a different area of the site.
