I usually do this through descendant CSS selectors. For example, for each page, I will give a unique ID to the body tag (generally based on the controller name) and each navigation element has a unique ID.
---- application.rhtml ----
<body id="<%= @controller.controller_name %>_body">
<ul> <li><a href="index" id="index_nav">Index</a></li> <li><a href="notes" id="notes_nav">Notes</a></li> </ul>
Assuming my controllers share the same name as the href, I would use CSS as follows to highlight the current navigation:
#index #index_nav, #notes #notes_nav { font-weight: bold; color: red }
Best Regards
Robin