Navigation can be the most frustrating part of websites for time-limited users. There should be a converse to that, but it would be more appropriate to say that good – even great – navigation should be so natural, users aren’t even really aware they are using it. Doesn’t that make sense?
A big part of natural navigation is establishing a natural hierarchy within the site. Using labeling that is the most common helps with this – “About Us”, “Products”, “Contact Us” are widely used and accepted as no-brainer labeling, and when you think about site navigation, you want readers to be focused on the product information, not on what a button or link really means.
As a web user, I prefer the navigation menus along the top in a shallow bar with scroll-over, dropdowns. That is most natural for me, but might not be so for every user to the site. A menu bar down the left side of the page, giving all available options is also a fast, user-friendly way to present navigation, but may not necessarily be the wisest use of space. This is a more traditional place to find navigation, so inexperienced visitors will still be able to find what they are looking for.
On site with fewer menu option, I think it best to go with horizontal menus. But in a case like The Home Depot, where there are dozens of navigation options and thousands of products, the left-side vertical navigation with vertical utilities bars is probably the best bet for ease of use.
Again, as I’ve stated many times recently, it all depends on the content and the users whether the navigation is subtle or overt, horizontal or vertical, simple or complex.