CSS Library: Horizontal CSS Menus: Here
Clean Arrow Underline Menu
Author: Dynamic Drive
This menu uses the nifty CSS Triangles technique to create a clean horizontal UL menu with a thick arrow border applied to the currently active menu item. It uses no images nor any extranous markup (thanks to CSS generated content) to accomplish the effect, and as a bonus, the menu can be easily aligned "left", "center", or "right' on the page. Cool!