oleg901,
<!DOCTYPE html>
<html lang="ru">
<head>
<meta charset="utf-8" />
<title>Документ без названия</title>
<style>
/* sleider3---------------------------------- */
#slide3{
width:400px;
height:400px;
margin:auto;
position: relative;
}
#img1{
margin:auto;
background-color:#7E6497;
width:400px;
height:400px;
position:absolute;
}
#img2{
margin:auto;
background-color:#D0FF00;
width:400px;
height:400px;
position:absolute;
}
#img3{
margin:auto;
background-color:#00C8FF;
width:400px;
height:400px;
position:absolute;
}
#img4{
margin:auto;
background-color:red;
width:400px;
height:400px;
position:absolute;
}
.of{
font-size: 70px;
line-height: 400px;
text-align: center;
opacity: 0;
z-index: 0;
transform: scale(0);
transition: 1.5s;
}
.active{
transition: 1s;
opacity: 1;
z-index: 100;
transform: scale(1);
}
</style>
</head>
<body>
<div id='an3'><header id="slide3">
<div id=slider>
<div id="img1" class="of">1</div>
<div id="img2" class="of">2</div>
<div id="img3" class="of">3</div>
<div id="img4" class="of">4</div>
</div>
<div id="levo1"></div>
<div id="pravo1"></div>
</header></div>
<script>
document.addEventListener('DOMContentLoaded', function() {
var Img = document.querySelectorAll(".of"),
ImgLength = Img.length,
ImgIndex = ImgLength - 1,
pause = 5000;
function show() {
Img[ImgIndex].classList.remove("active");
ImgIndex++;
ImgIndex %= ImgLength;
Img[ImgIndex].classList.add("active");
window.setTimeout(show, pause);
};
show()
});
</script>
</body>
</html>