var curIndex=0;
var timeInterval=3000;
var arr=new Array();
arr[0]="/flash/01.jpg";
//arr[1]="/flash/02.jpg";
//arr[2]="/flash/03.jpg";
//arr[3]="/flash/04.jpg";

setInterval(changeImg,timeInterval);
function changeImg()
{
    var obj=document.getElementById("obj");
    if (curIndex==arr.length-1) 
    {
        curIndex=0;
    }
    else
    {
        curIndex+=1;
    }
    obj.src=arr[curIndex];
}