tedster - 4:11 pm on Mar 20, 2011 (gmt 0)
Hello AmRes, and welcome to the forums.
.Nav defines a class. Because you are using an ID you may also need to define #Nav. I think that "specificity" rules are causing the ID to override the class.
To answer your direct question - no, HTML doesn't have that kind of functionality. It's basically about content and semantics, not presentation.