求一段倒计时JS代码

[laihongbo524]

如定义时间为30秒，倒计时到0后，弹出新窗口

[soonquick]

setTimeout(window.open(YouWindowUrl,'',''),30000);

[laihongbo524]

我的意思是，要求页面能显示倒计时的
我写的这段JS，又不报错，可没有效果，不知那错了

<script Language="JavaScript">
function Check(on){
if (on=="on")
{Layer1.style.display='';
showtime;}
else{Layer1.style.display='none';}
}

function showtime(){
var times=document.getElementById("sec")
var s=times-1;
times.innerHTML=s;
if (s=="0"){
Check("off");
window.open('x.asp');
}
setTimeout("showtime()",1000);
}
</SCRIPT>
<div id="Layer1" style="position:absolute;display:none;......略>
<span id="sec">30</span>
</div>
<a href="#" onclick="Check(on)">test</a>

[kingchang2000]

<script Language="JavaScript">
function Check(on){
if (on=="on")
{Layer1.style.display='';
showtime();
}
else{Layer1.style.display='none';}
}

function showtime(){
var times=parseInt(document.all.Layer1.innerText);
var s=times-1;
document.all.Layer1.innerText=s;
if (s=="0"){
Check("off");
window.open('x.asp');
}
setTimeout("showtime()",1000);
}
</SCRIPT>
<div id="Layer1"

style="position:absolute;display:none;......略>
<span id="sec">30</span>
</div>
<a href="#" onclick="Check('on')">test</a>