function clrTxt(controlid, textDefault) {
    if (document.getElementById(controlid).value == textDefault) {
        document.getElementById(controlid).value = "";
    }
}

function LUNCheck(src, arg) {

    number = arg.Value;

    var i, sum, weight;
    sum = 0;
    for (i = 0; i < number.length - 1; i++) {
        weight = number.substr(number.length - (i + 2), 1) * (2 - (i % 2));
        sum += ((weight < 10) ? weight : (weight - 9));
    }

    if (parseInt(number.substr(number.length - 1)) == ((10 - sum % 10) % 10)) {
        arg.IsValid = true;

    } else {

        //alert("Invalid card number");

        arg.IsValid = false;
    }

}