function Login(){
 if (document.loginForm.username.value == "") {
  alert("Please enter your user name.");
  return false;
 }
 if (document.loginForm.password.value == "") {
  alert("Please enter your password.");
  return false;
 }
 document.loginForm.response.value = hex_md5(document.loginForm.challenge.value+document.loginForm.password.value);
 document.loginForm.submit();
}