document.onkeydown=keyHit
if (document.layers) {
document.captureEvents(Event.KEYDOWN)
}
function keyHit(evt){
if (evt) {
thiskey = evt.which
}
else {thiskey = window.event.keyCode
}
if (thiskey==13){
ck();
return false;
}
}

function ck() {
var pp = 1;
for (var i=0; i < 14; i++) {
    if (document.cd.card.value.charAt(i) < "0"
	|| document.cd.card.value.charAt(i) > "9") {
	document.cd.card.value='11111111111111'
 //alert("sorry, card number entered is not valid");return false;
     }
    }
if (document.cd.card.value.charAt(0) > "0") {
document.cd.card.value='11111111111111'
  //alert("sorry, card number entered is not valid");return false;
   } 
if (document.cd.card.value.charAt(1) != "7"
&& document.cd.card.value.charAt(1) != "8") {
document.cd.card.value='11111111111111'
  //alert("sorry, card number entered is not valid");return false;
   } 
   //else
  document.cd.submit()
  return true
}