function countChars()
{
    var chars = $('smsMessage').get("value").trim().length;
    if (chars + 1 >= 160) {

        chars = 160;
        $('smsMessage').set("value", $('smsMessage').get("value").substring(0, 160));
    }

    $('smsMessageLeftChars').set('html', ' - rimanenti: <strong>' + (160 - chars) + '</strong>');
}

window.addEvent("domready", function() {

    if ($('smsMessage')) {

        countChars();
        window.addEvent("keyup", countChars);
    }
});