<script type="text/javascript" language="JavaScript">
    function validate_form()
    {
        var username = document.register.username;
        var password = document.register.password;
        var password_r = document.register.password_repeat;
        var e_name = document.register.email_name;
        var e_domain = document.register.email_domain;
        var e_ext = document.register.email_ext;
        var terms = document.register.accept_terms;

        if (username.value != '' && password.value != '' && password_r.value != '' && (e_name.value != '' && e_domain.value != '' &&  . e_ext.value != ''))
        {
            return document.register.submit.disabled = false;
        }

        return document.register.submit.disabled = true;
    }
    </script>