function validate()
{
var submitOK;
var ccnumber_01=document.getElementById("ccnumber_01").value;
var ccnumber_02=document.getElementById("ccnumber_02").value;
var ccnumber_03=document.getElementById("ccnumber_03").value;
var ccnumber_04=document.getElementById("ccnumber_04").value;

var ccname=document.getElementById("ccname").value;
var ccsurname=document.getElementById("ccsurname").value;
var ccchecksum=document.getElementById("ccchecksum").value;




if (document.user_form.paying_method[0].checked == true)
{
submitOK="true";

if (ccnumber_01.length<4 || ccnumber_02.length<4 || ccnumber_03.length<4 || ccnumber_04.length<4)
 {

 submitOK="false";
 }

if (submitOK=="false")
 {

alert("Bitte geben Sie eine gültige Kreditkartenangaben ein!");

 return false;
 }

}
}