var nav_items = document.getElementById('navigation').getElementsByTagName('a');
for(var i = 0; i < nav_items.length; i++) {
    var stripped_href = nav_items[i].href.match(/([^\/]+)\/$/)[1];
    if(document.location.href.match(stripped_href)) {
        nav_items[i].parentNode.className = 'selected';
        break;
    }
}