<script type="text/javascript">     
function countDown(secs,surl){     
//alert(surl);     
var jumpTo = document.getElementById('jumpTo');
jumpTo.innerHTML=secs;  
if(--secs>0){     
     setTimeout("countDown("+secs+",'"+surl+"')",1000);     
     }     
else{       
     location.href=surl;     
     }     
}     
countDown(5,'http://www.baidu.com/');
</script>

<span id="jumpTo">5</span>秒后自动跳转到

或者
<meta http-equiv="refresh" content="3; url='/' ">