// JavaScript Document
var Marquee = function(id){
    try{document.execCommand("BackgroundImageCache", false, true);}catch(e){};
    var container = document.getElementById(id),
    slide = container.getElementsByTagName("li")[0],
    speed = arguments[1] || 80,  //速度
    delta = 0,//当前滚动的位置
    critical = slide.offsetHeight;//临界点
    slide.innerHTML += slide.innerHTML;
    var rolling = function(){
      delta == -critical ? delta = 0 : delta--;
      slide.style.top = delta + "px";
    }
    var timer = setInterval(rolling,speed)//设置定时器
    container.onmouseover=function() {clearInterval(timer)}//鼠标移到marquee上时，清除定时器，停止滚动
    container.onmouseout=function() {timer=setInterval(rolling,speed)}//鼠标移开时重设定时器
  }
  window.onload = function(){
    Marquee("marquee");
  }