// set up popup callbacks
function hide(e)
{
    var popup = Event.element(e);
    if (popup.nodeName.toLowerCase() == 'img')
        popup = popup.parentNode;
    Element.hide($(popup));
}

function show(e)
{
    var link = Event.element(e);
    if (link.nodeName.toLowerCase() == 'img')
        link = link.parentNode;
    var popup = link.getAttribute('popup');
    Element.show($(popup));
}

function init()
{
    document.getElementsByClassName('popup').each(function(p)
    {
        Event.observe(p, 'click', hide, false);
    });
    document.getElementsByClassName('popuplink').each(function(l)
    {
        Event.observe(l, 'click', show, false);
    });    
}

Event.observe(window, 'load', init, false);