Sign Posts, Menus and the Information Tree

The Information Tree We often hear mention of an 'information tree' when it comes to the layout of a web site, but what exactly does that men.
The best analogue for a site's organisation is your public library.
Just think back: As you enter the library and before you confront the books themselves you will see a sign-post: 1.
New members Registration 2.
Admin Offices 3.
Reference Library 4.
Periodicals Room 5.
Lending Library.
These are the lower (main) branches of the library's information tree.
Once we enter the lending library we see categories of books there: a) Reference Books b) History c) Fiction d) Faith and Religion e) Etc In the fiction i.
Authors A -E ii.
Authors F- I iii.
Etc.
Using the Information Tree So looking for 'The Hound of the Baskervilles' in the lending library we would logical steps 1) Enter the lending library (5) 2) Look up fiction (c) 3) Go to Authors A-E People entering our website need the same clear sign-posting, and they need the sign-posting to be 'intuitive' ie self-evident.
Menus Menus are the equivalent of the sign-posts in the library.
The 'Main' menu needs to appear on virtually every page, normally part of the site 'header' and displayed horizontally.
In the case of our library model it would say "New Members Registry...
Admin Offices...
Reference Library...
" etc.
Clicking on any of these menu items (or links) should take the visitor to a 'Node Page', a page introducing the topic and containing links to the next level in the information tree.
So the node page for the lending library would at the very least have links to "Reference Books...
History...
Fiction" etc.
either in the form of lists with links or additional menus.
The fiction link, whatever its form, might take us through to a lower Node Page with its own explanatory matter and links to "Authors A-E...
Authors F-J" etc.

I say 'might' in this last case because what is called the three clicks rule.
Received Wisdom says that visitors are unwilling to 'click' more than three times to find what we want, and though to date we have only clicked three times we haven't yet located 'The Hound of the Baskervilles'.
So our listing might be more detailed "Fiction: Authors A-E"

Shortcuts and Icons So how do major sites get round the 'three clicks' rule.
We can do worse than look ar Amazon's landing page.
It is a dense matrix of Icons, small images, each linking to complete sections of the site.
Clicking on an Icon of a washing machine we are taken through what would be several menu steps direct to our target.
The classic layout of a CMS site with the Landing Page a matrix of tasters leading to nodes further up the tree allows the visitor to jump two or three levels of menus and nodes to reach his target page.
Simpler still the site "Search" facility can achieve the same provided that your information tree is properly planned from the outset.