<SCRIPT LANGUAGE="JavaScript"> 
<!-- 
var maxtime = 60*60 //一个小时,按秒计算,自己调整! 
function CountDown(){ 
if(maxtime>=0){ 
minutes = Math.floor(maxtime/60); 
seconds = Math.floor(maxtime%60); 
msg = "距离结束还有"+minutes+"分"+seconds+"秒"; 
document.all["timer"].innerHTML=msg; 
if(maxtime == 5*60) alert('注意,还有5分钟!'); 
--maxtime; 

else{ 
clearInterval(timer); 
alert("时间到,结束!"); 


timer = setInterval("CountDown()",1000); 
//--> 
</SCRIPT> 
<div id="timer" style="color:red" mce_style="color:red"></div>