Just use the :not operator in CSS and exclude the first nav from second nav css definition.
Add a class to firstNav, and then inside the css use :not like so
nav ul:not(.first)
Edit
Check the fiddle again. Seems like there is another trick to do this, something called a substring matching . Note that the order of the css in the fiddle is important. if you flip the definitions of the navs, the css will not work. I haven't tested this in IE 8, but based on what I read, it should work in IE8 as well.
Fiddle