Need more interactivity in nav menu

You need to use either javascript or server-side scripting code like PHP to determine what page the user is on or which menu item was last clicked and apply a different CSS class to the appropriate menu item.  

Here's an idea or two to get you started:

http://www.richnetapps.com/automatically_highlight_current_page_in/
http://www.paulund.co.uk/use-jquery-to-highlight-active-menu-item

I was afraid you'd say that.

Create a class for your nav for current page.

header nav ul li.currentpage a {
      color:red;
    text-decoration:underline
}

Then in your li add the class currentpage

 <li class="currentpage"><a href="index.html">home</a></li>

http://jsbin.com/umitig/1/

Play around with the actual color you want and also a hover feature too