var ann = document.getElementById("ann");
var ann1 = document.getElementById("ann1");
var ann2 = document.getElementById("ann2");
var speed=50;    //滚动速度值，值越大速度越慢
ann2.innerHTML = ann1.innerHTML;   //克隆ann2为ann1
function Marquee(){
	if(ann2.offsetTop-ann.scrollTop<=0)    //当滚动至ann1与ann2交界时
		ann.scrollTop-=ann1.offsetHeight;    //ann跳到最顶端
	else{
		ann.scrollTop++;
	}
}
var MyMar = setInterval(Marquee,speed);        //设置定时器
ann.onmouseover = function(){clearInterval(MyMar)}    //鼠标经过时清除定时器达到滚动停止的目的
ann.onmouseout = function(){MyMar = setInterval(Marquee,speed)}    //鼠标移开时重设定时器