The Energon Pub

I'm in the last class of a web development degree and the client has specified an interest in having a simple to maintain website for a charity event.

How do I create a horizontal submenu using HTML and CSS? By submenu I mean something like the menu on this site, but instead of the submenu being a drop-down menu, the client wants the submenu to display as a second horizontal bar. I don't want to use JavaScript unless it's necessary, like for browser compatibility, although I like the idea of using a JavaScript insert so I only have to maintain one file that the rest of the site can look up.

Any suggestions?