function validate_form ( )
{
    valid = true;
    if ( document.loginform.username.value == "" )
    {
        alert ( "Please fill in your Username!" );
        valid = false;
    }
    else if ( document.loginform.password.value == "" )
    {
        alert ( "Please fill in your password!" );
        valid = false;
    }
    return valid;
}