window.onload=tab;

function tab(){

var n=0;

var timer=null;

var div1=document.getElementById("div1");

var div2=document.getElementById("div2");

var div3=div1.getElementsByTagName("li");

var div4=div2.getElementsByTagName("div");

timer=setInterval(function(){

n++;

if(n>=div3.length){

n=0;

}

for(var i=0;i<div3.leght;i++){

div3[i].className="";

div4[i].style.display="none"

}

div3[n].className="active";

div4[n].style.display="block"

},2000)

}