I recently encountered 2 clients that wanted vertical navigation. Why do they want vertical navigation is my question? That is beyond me. Well, anyway, I would like to share this excellent article on why you should not use vertical navigation on your website. Yes there are some exceptions but for the most part horizontal navigation has been tested and perfroms better usuability for the user. I would in fact consider it for a minimalist effect on a website or extremely heavy navigation with a lot of pages, other than that I think vertical is the key navigation. In fact think it looks much nicer as well. So if you are considering vertical navigation for your website, please read this article by Smashing Magazine and reconsider your website design and navigation.