var cur_index=1
            var num=3 //该值记录标签的个数
            var settime
            function GetObj(objName){
             if(document.getElementById){
              return eval('document.getElementById("' + objName + '")');
             }else if(document.layers){
              return eval("document.layers['" + objName +"']");
             }else{
              return eval('document.all.' + objName);
             }
            }
            function change_Menu(index){
             for(var i=1;i<=num;i++){
              if(GetObj("con"+i)&&GetObj("m"+i)){
               GetObj("con"+i).style.display = 'none';
               GetObj("m"+i).className = "menu"+i+"Off";
              }
             }
             if(GetObj("con"+index)&&GetObj("m"+index)){
              GetObj("con"+index).style.display = 'block';
              GetObj("m"+index).className = "menu"+index+"On";
             }
             cur_index=index
             if(cur_index<num){
                cur_index++
               }
             else{
                 cur_index=1
               }
             settime=setTimeout("change_Menu(cur_index)",8000)//设置延迟时间
              
            }
            function Menu(c_index){
              clearTimeout(settime)
              change_Menu(c_index)
             }