var isStart=true;
var nn;
var tt;
var bPlay=new Image;
function pre_img(){
resetPlay();
nn--;
if(nn < 1) nn=3;
setFocus(nn);
}
function next_img(){
resetPlay();
nn++;
if(nn > 3) nn=1;
setFocus(nn);
}
function change_img()
{
if(isStart){
 nn++;
 if(nn>3) nn=1;
 setFocus(nn);
 }else{
 tt=setTimeout('change_img()',100);
 }
}
function setFocus(i)
{
 if(tt) clearTimeout(tt);
 nn = i;
 selectLayer1(i);
tt=setTimeout('change_img()',4000);
}
function selectLayer1(i)
{
 switch(i)
 {
 case 1:
document.getElementById("bbs_s1").style.display="block";
document.getElementById("bbs_s2").style.display="none";
document.getElementById("bbs_s3").style.display="none";
 break;
case 2:
document.getElementById("bbs_s1").style.display="none";
document.getElementById("bbs_s2").style.display="block";
document.getElementById("bbs_s3").style.display="none";
 break;
 case 3:
document.getElementById("bbs_s1").style.display="none";
document.getElementById("bbs_s2").style.display="none";
document.getElementById("bbs_s3").style.display="block";
 break;
 }
}