404 에러 코드

<?
include_once("_common.php");
$year = $_GET['year'];

$month_sql = "SELECT DISTINCT wr_month FROM g5_write_history WHERE wr_year = '$year' ORDER BY wr_month DESC";
$month_result = sql_query($month_sql, true);

for ($i = 0; $month_row = sql_fetch_array($month_result); $i++){
?>
<li <? if ($i % 2 == 0){ echo "class='left_history'"; } else if ($i % 2 == 1) { echo "class='right_history'"; }?>>
    <h2><?=$year?>.<?=$month_row['wr_month']?></h2>
    <?
    $sql = "SELECT * from g5_write_history WHERE wr_year = '$year' AND wr_month = '$month_row[wr_month]' ORDER BY wr_sort DESC";
    $result = sql_query($sql, true);

    while ($row = sql_fetch_array($result)){
    ?>
    <p>
        <? if ($is_admin){ ?>
        <a href="<?=G5_BBS_URL?>/write.php?bo_table=history&wr_id=<?=$row['wr_id']?>&w=u">
        <? } ?>
        <span><?=$row['wr_content']?></span>
        <? if ($is_admin){ ?>
        </a>
        <? } ?>
    </p>
    <?
    }
    ?>
</li>
<?
}
?>