회원가입 새창 클릭시 팝업띄우려고 하는데 오류가 납니다.
아래 소스 입니다. 답변좀 부탁드립니다.

<?
if (!defined("_GNUBOARD_")) exit; // 개별 페이지 접근 불가
?>

<script type="text/javascript" language=JavaScript>
var bReset = true;
function chkReset(f)
{
    if (bReset) { if ( f.mb_id.value == '아이디' ) f.mb_id.value = ''; bReset = false; }
    document.getElementById("pw1").style.display = "none";
    document.getElementById("pw2").style.display = "";
}
</script>
<style>
.login_input { border:1px solid #CCCCCC; height:18px; width:100px;}
</style>
<!-- 로그인 전 외부로그인 시작 -->
<table cellpadding="0" cellspacing="0">
<form name="fhead" method="post" action="javascript:fhead_submit(document.fhead);" autocomplete="off">
<input type="hidden" name="url" value="<?=$urlencode?>">
    <tr>
        <td>
            <table cellpadding="0" cellspacing="0">
                <tr>
                    <td><input name="mb_id" type="text" maxlength="20" required itemname="아이디" value='아이디' onMouseOver='chkReset(this.form);' onfocus="this.value=''" class='login_input'></td>
                </tr>
                <tr>
                    <td width="100" id=pw1><input type="text" maxlength="20" required itemname="패스워드" value='●●●●' onMouseOver='chkReset(this.form);' onfocus='chkReset(this.form);' class='login_input'></td>
<td id=pw2 style='display:none;' width="100"><input name="mb_password" type="password" maxlength="20" required itemname="패스워드" onMouseOver='chkReset(this.form);' onfocus='chkReset(this.form);' class='login_input'></td>
                </tr>
            </table>
</td>
        <td width="40" height="50"><input type="image" src="<?=$outlogin_skin_path?>/img/login.gif" width="40" height="50"></td>
    </tr>
    <tr>
        <td width="140" colspan="2">
 <table cellpadding="0" cellspacing="0" height="33">
                <tr>
                    <td width="67" height="33"><a href="javascript:win_password_lost();"><img src="<?=$outlogin_skin_path?>/img/id_pw.gif" width="67" height="5" border="0"></a></td>
                    <td width="45" height="33"><div align="right"><a href="javascript:na_open_window('member', '<?=$g4[bbs_path]?>/register.php', 0, 0, 300, 200, 0, 0, 0, 1, 0);" target="_self"><img src="<?=$outlogin_skin_path?>/img/join.gif" width="59" height="5" border="0"></a></div></td>
    </tr>
</table>
  </td>
    </tr>
</table>
</form>

<script language="JavaScript">
function fhead_submit(f)
{
    f.action = "<?=$g4[bbs_path]?>/login_check.php";
    f.submit();
}
</script>
<!-- 로그인 전 외부로그인 끝 -->