function addOnLoadEvent(func) {
    var oldonload = window.onload;
    if (typeof window.onload != 'function') {
        window.onload = func;
    } else {
        window.onload = function() {
            if (oldonload) {
                oldonload();
            }
            func();
        }
    }
}

function imgSwap(imgObject, swapSrc) {
    $(imgObject).src = swapSrc;
}

function prepareMenu() {
    // add hover (as class) to list items, for browsers that don't support this feature by default
    var main_menu_lis = $('main_menu').getElementsByTagName('li');
    for (var i = 0, len_i = main_menu_lis.length; i < len_i; i++) {
        $(main_menu_lis[i]).onmouseover = function() {
            this.addClassName('hover');
        }
        $(main_menu_lis[i]).onmouseout = function() {
            this.removeClassName('hover');
        }
    }
    var sub_items = $$('div.subItem');
    for (var i = 0, len_i = sub_items.length; i < len_i; i++) {
        $(sub_items[i]).onmouseover = function() {
            this.addClassName('hover');
        }
        $(sub_items[i]).onmouseout = function() {
            this.removeClassName('hover');
        }
    }
    var subsub_items = $$('div.subsubItem');
    for (var i = 0, len_i = subsub_items.length; i < len_i; i++) {
        $(subsub_items[i]).onmouseover = function() {
            this.addClassName('hover');
        }
        $(subsub_items[i]).onmouseout = function() {
            this.removeClassName('hover');
        }
    }
}

// execute when page is loaded
addOnLoadEvent(prepareMenu);