By default asp.net menu webcontrol is rendering as html "table". This makes difficult to customize menu with CSS .

You could use ASP.NET 2.0 CSS Friendly Control Adapters 1.0 to render menu as html "ul" tags, but there are  some bugs(over 50) at this moment.

 Also I ecountered a menu problem when browsing with IE 6 and using css adapters, simply my menus were not appearing!?

So, the easiest way is using RadMenu control from telerik.com.

My latest website http://apartamente-garsoniere.ro is using a trial version of RadMenu control. And I'm trying to get more points from telerik in order to buy this control