function add_nav_listeners() {
    var left_nav = document.getElementById('left-nav');
    
    var links = left_nav.getElementsByTagName('A');
    
    for( var i=0; i < links.length; i++ ) {
        var l = links[i];
        if( l.href.charAt( l.href.length - 1) == '#' ) {
            l.onclick = function(){ change_state(this); return false;}
        }
    }
}

function change_state( node ) {
    var visible = null;
    if( node.parentNode.className.match(/active-children/) > -1) {  
        node.parentNode.className = node.parentNode.className + " active active-children";
    } else {
        node.parentNode.className = node.parentNode.className.replace(/active-children/, '')
        node.parentNode.className = node.parentNode.className.replace(/active/, '')
    }
}


window.onload = add_nav_listeners