The asp:menu control makes building a website Menu simple. It is a powerful control that has over 75 properties which can be applied declaratively to construct complex static and dynamic menus. Despite it's ease of use, it has a few deficiencies that ASP.NET developers should be aware of. There are known issues with it in IE 8 and Safari browsers.
Thankfully, there is a official patch for IE 8 and workaround for Safari to correct the rendering issues.
Related:
HOW TO suppress the popout arrow on the menu while using ASP.NET 2.0 Menu control
HOW TO build a simple Tab Menu Control