function accordion(el) {
    if (Element.hasClassName(el.parentNode.id+'-body','visible')){
        //do not need to perform an actions
        return;
    }
    var eldown = el.parentNode.id+'-body';
    var apanels = document.getElementsByClassName('panelBody',el.parentNode.parentNode);
    
    for (var i=0;i<apanels.length;i++){
        if (Element.hasClassName(apanels[i].parentNode.id+'-body','visible'))
            var elup = apanels[i].parentNode.id+'-body';
    }

    new Effect.Parallel([ new Effect.SlideUp(elup), new Effect.SlideDown(eldown) ], {duration: 0.5});
    Element.removeClassName(elup,'visible');
    Element.addClassName(eldown,'visible');
}

//pass in ID of container element that has all instances of apanels
function accordion_init(id) {
    var apanels = document.getElementsByClassName('panelBody',id);
    for (var i=0;i<apanels.length;i++){
        apanels[i].style.display = 'none';
    }
    var velems = document.getElementsByClassName('visible');
    for (var i=0;i<velems.length;i++){
        $(velems[i]).style.display = 'block';
    }
}
function addEvent(elm, evType, fn, useCapture) {
    elm["on"+evType]=fn;return;
}

addEvent(window, "load", function(){accordion_init('left_menu');});