var filter_mail       = /^([\w-]+(?:\.[\w-]+)*)@((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,6}(?:\.[a-z]{2})?)$/i;
var alert_string      = "All mandatory fields must be field in.";
var alert_mail        = "Please enter a valid email address.";
var alert_wrong_pass  = "Passwords do not match. Try again.";
var alert_little_pass = "The password must be at least 5 characters";
var confirm_delete    = "Confirm delete?";

function check_mandatory_fields(sender)
{
  for (i = 0; i < sender.elements.length; i++)
  {
    if (sender.elements[i].className == "field_zirka")
    {
      if (sender.elements[i].value.length < 1)
      {
        alert (alert_string);
        sender.elements[i].focus();
        return false;
      }
      if (sender.elements[i].name == "mail")
      {
        if (!filter_mail.test(sender.elements[i].value))
        {
          alert(alert_mail);
          sender.elements[i].focus();
          return false;
        }
      }
      if (sender.elements[i].type == "password")
      {
        if (sender.elements[i].value.length < 5)
        {
          alert(alert_little_pass);
          sender.elements[i].focus();
          return false;
        }
        if (sender.confirm_password)
        {
          if (sender.confirm_password.value != sender.elements[i].value)
          {
            alert(alert_wrong_pass);
            sender.confirm_password.focus();
            return false;
          }
        }
      }
    }
  }
    return true;
}