<!--// Credit card validation functions.function isCreditCard(st) {  // Encoding only works on cards with less than 19 digits  if (st.length > 19)    return (false);  sum = 0; mul = 1; l = st.length;  for (i = 0; i < l; i++) {    digit = st.substring(l-i-1,l-i);    tproduct = parseInt(digit ,10)*mul;    if (tproduct >= 10)      sum += (tproduct % 10) + 1;    else      sum += tproduct;    if (mul == 1)      mul++;    else      mul--;  }  if ((sum % 10) == 0)    return (true);  else    return (false);} // END FUNCTION isCreditCard()function isVisa(cc){  if (((cc.length == 16) || (cc.length == 13)) &&      (cc.substring(0,1) == 4))    return isCreditCard(cc);  return false;}  // END FUNCTION isVisa()function isMasterCard(cc){  firstdig = cc.substring(0,1);  seconddig = cc.substring(1,2);  if ((cc.length == 16) && (firstdig == 5) && ((seconddig >= 1) && (seconddig <= 5)))    return isCreditCard(cc);  return false;} // END FUNCTION isMasterCard()function isAmericanExpress(cc){  firstdig = cc.substring(0,1);  seconddig = cc.substring(1,2);  if ((cc.length == 15) && (firstdig == 3) && ((seconddig == 4) || (seconddig == 7)))    return isCreditCard(cc);  return false;} // END FUNCTION isAmericanExpress()function isDinersClub(cc){  firstdig = cc.substring(0,1);  seconddig = cc.substring(1,2);  if ((cc.length == 14) && (firstdig == 3) && ((seconddig == 0) || (seconddig == 6) || (seconddig == 8)))    return isCreditCard(cc);  return false;}function isCarteBlanche(cc){  return isDinersClub(cc);}function isDiscover(cc){  first4digs = cc.substring(0,4);  if ((cc.length == 16) && (first4digs == "6011"))    return isCreditCard(cc);  return false;} // END FUNCTION isDiscover()function isEnRoute(cc){  first4digs = cc.substring(0,4);  if ((cc.length == 15) && ((first4digs == "2014") || (first4digs == "2149")))    return isCreditCard(cc);  return false;}function isJCB(cc){  first4digs = cc.substring(0,4);  if ((cc.length == 16) &&      ((first4digs == "3088") ||       (first4digs == "3096") ||       (first4digs == "3112") ||       (first4digs == "3158") ||       (first4digs == "3337") ||       (first4digs == "3528")))    return isCreditCard(cc);  return false;} // END FUNCTION isJCB()function isAnyCard(cc){  if (!isCreditCard(cc))    return false;  else if (!isMasterCard(cc) && !isVisa(cc) && !isAmericanExpress(cc) && !isDinersClub(cc) &&      !isDiscover(cc) && !isEnRoute(cc) && !isJCB(cc)) {    return false;  }  return true;} // END FUNCTION isAnyCard()function checkit(cc){	if (!isAnyCard(cc)) {		alert('Your credit card number appears to be incorrect.\r\rPlease re-enter it.');		return false;	}}//-->