<script>

            var picarr=[

                "pic/lb1.jpg",

                "pic/lb2.jpg",

                "pic/lb3.jpg",

                "pic/lb4.jpg"

            ];

            //全局变量index控制当前所在第几张图片

            var index=;

            var timer;

            var radiobtn= document.getElementsByClassName("tubiao")[].getElementsByTagName("span");

            function  autochang(index) {

                var index=parseInt(index);

                document.getElementsByClassName("content_1")[].style.backgroundImage="url("+picarr[index]+")";

                for(var j=;j<radiobtn.length;j++){

                    radiobtn[j].className="";

                }

                radiobtn[index].className="actived";

            }

            function change(index){

                setInterval("autochang((index++)%radiobtn.length);",);

            }

            //页面加载成功初始效果

            change(index);

            //当鼠标点击点点的时候切换效果

              for(var i=;i<radiobtn.length;i++){

               radiobtn[i].index = i;

                radiobtn[i].onclick=function () {

                    clearInterval(timer);

                   autochang(this.index);

                   index=this.index;

                }

             }

             //点击左箭头

             document.getElementsByClassName("left_jiantou")[].onclick=function(){

                 index--;

                 if(index<){

                     index=radiobtn.length-;

                 }

                 autochang(index);

             }

             //点击右箭头

             document.getElementsByClassName("right_jiantou")[].onclick=function(){

                 index++;

                 if(index>=radiobtn.length){

                     index=;

                 }

                 autochang(index);

             }

    </script>