See the standard horizontal navigation pattern for implementation notes.
Adding secondary navigation in the form of a vertical drop-down is a two step process:
ux-hnav-has-horizontal-secondary to the main ul.ul within the list item for the proper tab (see source for example).©2015 - Matt Lavallee - Senior UI/UX Designer Lorem ipsum dolor sit amet, consectetur adipiscing elit. Aenean tincidunt ligula dui, ut sodales tortor. Integer cursus, nisl a aliquet congue, diam metus dapibus risus, eget lacinia sapien est in mauris. Maecenas et neque sed neque tristique commodo id non massa. Aliquam eget egestas neque. Suspendisse mauris nisl, accumsan sit amet ullamcorper sed, tincidunt at justo.