This is a drop-down menu that is using only CSS (although some Javascript is required for Internet Explorer). It can be either vertical or horizontal.
The code we have inserted in the template that this page is using is simply {menu template='cssmenu.tpl'}.
You style the menu in the stylesheet Navigation: CSSMenu - Horizontal or Navigation: CSSMenu - Vertical for the vertical CSSMenu.
But to be on the safe side, copy this stylesheet and attach the new stylesheet to the template instead (and make your changes in the new stylesheet). Then you can always revert to the default stylesheet if something goes wrong.