What is still a big question for me , is whether to position the main menu vertically in the left column or horizontally at the top of the page. I'm a usability consultant in Holland, do a lot of eyetracking research and of course read a lot of resuarch that is being done, but I can't really find a good answer to that question supported by research. I think they're both working wel, but have never found good comparing research. Has anyone?

Personally the trend feels like top navigation for the main categories and side navigaiton for second-third level content to avoid scrolling while navigation.

I personally believe that most users expect for a top menu to exist.

If a top horizontal menu wouldn't exist, I'm sure users would notice. If a side vertical menu doesn't exist, most of users wouldn't notice (or feel the need for one).

My current thinking is to keep the to main site navigation within a horizontal, somewhere in the header, with secondary navigation sitting below - depending on requirements/context.

I tend to use a left navigation for catalogue type sites, utilising it for product list/groups. This way you can separate site navigation from catalogue navigation.

In my opinion, vertical navigation is much more clear. Elements are located close to each other, combining a noticeable block. Navigation is a list, and you have to agree that bullet-type vertical lists in the books are much easier to read than long comma-separated lists.

But, I have to admit that if there are few elements on the list, horizontal is the only option. Why making vertical list for "posts, about, contact"? It would just steal valuable content space.

There is no right/wrong navigation type -- it's up to you to decide what works best with your particular design. After all, design isn't purely science, there is an element of preference involved that makes it your own.

Having said this, there are some advantages/disadvantages to both types. For example, as Supercharged says vertical menus are slightly clearer. This is because they're faster to scan (provided the contents are left aligned). Your eye can move down the menu quickly as the text for each item begins in the same place. Not so with horizontal navigation where the items are spaced out unevenly. Also, vertical navigation can generally accomodate more items.

This doesn't mean horizontal navigation is "worse". Horizontal navigation doesn't take much vertical space, so you can stick it on top of the site where it's out of the way, yet occupying a prominent location.

Louis Lazaris covers this subject quite nicely over at smashingmagazine.com - The Case Against Vertical Navigation http://bit.ly/7avxaO

Thank you all for your reactions. There probably just isn't much research on this topic and I think I agree with the arguments in favour of horizontal navigation in many cases. I think one of the best arguments then is that horizontal navigation is seen and understood well, while it leaves the very important space on the left side available for important calls to action, which is almost alway seen by visitors as I usually find in the eyetracking research I do.

Hello, according with the last interface book I've read, horizontal menu is used to make a global navigation and left menu for categories...

But for me doesn't exist a right way to design a menu, sometimes works well and other times no! For each project needs a different way to solve the problems.