function hiLite(el) {
    if (el.src.indexOf('_hl.') == -1) {
        el.src = el.src.substring(0, el.src.length - 4) + '_hl' + el.src.substring(el.src.length - 4, el.src.length);
    }
}

function deHiLite(el) {
    if (el.src.indexOf('_hl.') != -1) {
        el.src = el.src.substring(0, el.src.length - 7) + el.src.substring(el.src.length - 4, el.src.length);
    }
}

function onlyNumbers(evt) {
    var e = event || evt; // for trans-browser compatibility
    var charCode = e.which || e.keyCode;

    if (charCode > 31 && (charCode < 48 || charCode > 57))
        return false;

    return true;
}