function loadMenu(e) {
    function mouseOverMenu(e) {
        var elem = this;
        var image = elem.childNodes[0].src;
        var exp = new RegExp(".jpg");
        elem.childNodes[0].src = image.replace(exp, "_o.jpg");
    }
    function mouseOutMenu(e) {
        var elem = this;
        var image = elem.childNodes[0].src;
        var exp = new RegExp("_o.jpg");
        elem.childNodes[0].src = image.replace(exp, ".jpg");
    }
    
    var menuItems = YAHOO.util.Dom.getElementsByClassName("menuitem", "a");
    
    for(var i=0;i<menuItems.length;i++)
    {
        YAHOO.util.Event.addListener(menuItems[i], "mouseover", mouseOverMenu);
        YAHOO.util.Event.addListener(menuItems[i], "mouseout", mouseOutMenu);
    }
}

YAHOO.util.Event.addListener(window, "load", loadMenu);