下载网站打开页面后间隔多少时间才显示下载链接地址的代码

<a id="readylink" href="javascript:download();" class="submitbutton">请等待</a>
<a id="downloadlink" href="http://www.jb51.net/" class="submitbutton" style="display:none;">下载</a>

<script type="text/javascript">
var timeout="25";
function countdown()
{
if (timeout<=0)
{
document.getElementById("readylink").style.display="none";
document.getElementById("downloadlink").style.display="block";
}
if (timeout>0)
{
document.getElementById("readylink").innerHTML=请稍等+timeout+秒;
setTimeout("countdown()",1000);
}
timeout--;
}
countdown();

function download() {
if(timeout>0) {
alert(请稍等，服务器正在取得相关资源 。);
}
}
</script>