<!DOCTYPE html>
<html>
<head>
<style>div {
background-image: url('smiley.gif');
background-repeat: no-repeat;
width: 400px;
height: 400px;
border: 1px solid #000000;
}
</style>
</head>
<body>
<button type="button" onclick="myFunction()">Position background image</button>
<br>
<div id="myDiv">
</div>
<script>
function myFunction() {
document.getElementById("myDiv").style.backgroundPosition = "center bottom";
}
</script>
</body>
</html>