function login() {
  var loginForm = document.getElementById("loginForm");
  if (loginForm.username.value == "") {
      alert("Husk at indtaste brugernavn.");
      return false;
  }
  if (loginForm.password.value == "") {
      alert("Husk at indtaste adgangskode.");
      return false;
  }
  var submitForm = document.getElementById("submitForm");
  submitForm.username.value = loginForm.username.value;
  submitForm.response.value = hex_md5(loginForm.challenge.value+loginForm.password.value);
  submitForm.submit();
}