function rollover(id) {
        document.getElementById(id).src = "./images/nav/topnav_"+id+"-over.gif";
}

function rollout(id) {
        document.getElementById(id).src = "./images/nav/topnav_"+id+".gif";
}

function rollover2(id, ext) {
        document.getElementById(id).src = "./images/nav/topnav_"+id+"-over" + ext;
}

function rollout2(id, ext) {
        document.getElementById(id).src = "./images/nav/topnav_"+id+ ext;
}