<SCRIPT LANGUAGE="
javascript"> 
<!-- 
var maxtime = 60*60;//60*60 //一个小时,按秒计算 
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"; 
msg = "距离结束还有"+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!"); 
maxtime=60*60; 
timer = setInterval("CountDown()",1000); 
} 
} 
timer = setInterval("CountDown()",1000); 
//--> 
</SCRIPT> 
<div id="timer" style="color:red"></div>