html部分

<span value="1397145180" style="line-height:200%;"></span>

js部分

<script type="text/javascript">    
    $(document).ready(function(){    
        setInterval(function(){         
        $(".time_wrap").each(function(){    
            var Obj = this;        
            var EndTime = new Date(parseInt($(Obj).attr('value')) * 1000);    
            var NowTime = new Date();    
            var nMS=EndTime.getTime() - NowTime.getTime();    
            var nD=Math.floor(nMS/(1000 * 60 * 60 * 24));    
            var nH=Math.floor(nMS/(1000*60*60)) % 24;    
            var nM=Math.floor(nMS/(1000*60)) % 60;    
            var nS=Math.floor(nMS/1000) % 60;    
            var nMS=Math.floor(nMS/100) % 10;    
            if(nD>= 0){         
                var str = '<span ><em>'+nD+'</em>天<em>'+nH+'</em>小时<em>'+nM+'</em>分<em>'+nS+'.'+nMS+'</em>秒</span>';    
                $(Obj).html(str);    
            }         
            });    
        }, 100);
    }); 
</script>