function ShowRollover(imageName) {
    var img = document.getElementById(imageName);
    if (img.src.indexOf('_def') != -1) {
        var s = img.src, l = s.length, e = s.substring(l - 4, l);
        img.src = s.substring(0, l - 8) + '_ovr' + e;
        img.longdesc = "active"
    }
}

function HideRollover(imageName) {
    var img = document.getElementById(imageName);
    if (img.longdesc != null) {
        if ((img.src.indexOf('_ovr') != -1) && (img.longdesc.indexOf("active") != -1)) {
            var s = img.src, l = s.length, e = s.substring(l - 4, l);
            img.src = s.substring(0, l - 8) + '_def' + e;
        }
    }
}