How to add custom classes to navigation
PermalinkExample: change <li>About</li> to <li class="about">About</li>
I have been using the following global to display my nav within 'elements/header.php' in the Plain Yogurt theme:
$a = new GlobalArea('Header Nav');
$a->display($c);
Any advice or links to a similar thread that I couldn't find would be great. Thanks in advance.

http://c5blog.jordanlev.com/blog/2011/12/customizing-the-autonav-te...
Putting different classes on different menu items is actually not a common thing to do -- the point of a CMS and an auto-generated menu is to have a system where users can add new pages and rearrange the order whenever they want, without having to call up a designer or developer to make changes. As such, the primary navigation menu should really be designed with flexibility in mind, and not have "hard-coded" styles.