Good navigation is vital for a well-crafted web site and closely linked to how the site is organised. Think through what should be where, and then think how your visitors should move about your site. It should be as easy as possible, simple and clear, and consistent. The worst kind of navigation is that which changes position on the page or loses some of its components when moving to a different page.

Good navigation systems feature the capacity to expand in some way. This may be visual or may be in the form of a secondary navigation layer, complementary to the primary links. The best expanding systems enable the use to easily see the route they have taken from the home page to their current location. The exit route should be clear, usually with a single click to the home page.

If the site is large it should have some local search facility on it. This enables visitors to find relavent pages quickly. Also worth considering are drop down menus, so visitors, again, can quickly find the information they want. Graphics used in navigation systems should be clear. Low quality graphics or unreadable text are next to useless.

Navigation doesn't have to be complex and versitility is important. For an excellent example check out BBC News Online.