Event.observe(document, 'dom:loaded', function(event) {
    $$('#pageNavUp .container-navigation-trigger').each(function (item) {
        item.observe('click', function(event) {
            event.stop();
            targetEl = item.id.replace('containerTriggerpageNavUp', 'containerTargetpageNavUp');
            $$('#pageNavUp .container-navigation-target').invoke('hide');
            $$('#pageNavUp .container-navigation-trigger').invoke('hide');
            $(targetEl).show();
            $$('#pageNavUp .container-navigation-trigger').each(function(elem) {
                    if(elem.id != item.id) {
                        $(elem).show();
                    }
            });

        });
    });
    $$('#pageNavDown .container-navigation-trigger').each(function (item) {
        item.observe('click', function(event) {
            event.stop();
            targetEl = item.id.replace('containerTriggerpageNavDown', 'containerTargetpageNavDown');
            $$('#pageNavDown .container-navigation-target').invoke('hide');
            $$('#pageNavDown .container-navigation-trigger').invoke('hide');
            $(targetEl).show();
            $$('#pageNavDown .container-navigation-trigger').each(function(elem) {
                    if(elem.id != item.id) {
                        $(elem).show();
                    }
            });

        });
    });
});