404页面上常用到倒计时返回指定页面，下面是jquery和php结合倒计时返回指定页面，代码如下：

<?php
$url=”http://zhoumo123.cn/“;
$num=”10″;
?>

<script type="text/javascript"  src="js/jquery-1.8.3.min.js"></script>
<script type="text/javascript">
var gcisNum = <?php echo $num; ?>;
$(function(){
    gcisSetNum();
});

function skipNum()
{

	$("#skip").html(gcisNum-1);
	gcisNum--;
	if(gcisNum)
	{
		gcisSetNum();
	}
	else
	{
	    window.location='<?php echo $url; ?>';
	}
}

function gcisSetNum()
{
	setTimeout("skipNum()", 1000);
}

</script>

<div>系统在&nbsp;<span id="skip"><?php echo $num; ?></span>&nbsp;秒后自动跳转到首页。</div>