css中常见几种float方式
http://jingyan.baidu.com/article/72ee561a670269e16138dfd5.html
<script type="text/javascript"> var maxtime; if(window.name==''){ maxtime=1*60; } else{ maxtime=window.name; } function CountDown(){ if(maxtime>=0){ minutes=Math.floor(maxtime/60); seconds=Math.floor(maxtime%60); msg="距离倒计时结束还有:"+minutes+"分"+seconds+"秒"; document.all["timer"].innerHTML=msg; if(maxtime==zsj*60){ alert('考试正式开始'); } --maxtime; window.name=maxtime; } else{ clearInterval(timer); $(".btn").css("display","none"); alert("考试已经结束了"); } } timer=setInterval("CountDown()",1000); </script>