The CSS "sliding doors" technique allows you to create sophisticated tabs for your menus. Sadly, WordPress doesn't allow you to use a <span> element in the wp_list_pages() and wp_list_categories() functions.
In order to achieve this very cool menu, you first need to have a bit of knowledge about the CSS sliding doors technique, and the necessary images.
If you need to know more about this technique, you should consider reading this article: http://www.alistapart.com/articles/slidingdoors/
If you don't already know this awesome technique here's a quick example to get you started:
Let's start by building a typical navigation list:
<ul id="nav"> <li><a href="#">link n°1</a></li> <li><a href="#">link n°2</a></li> <li><a href="#">link n°3</a></li> </ul>
If we use CSS to apply background images to our links in order to make this menu look prettier...