<!DOCTYPE html>
<html>
<head>
<style>body {
background: #f3f3f3 url('img_tree.png');
}
</style>
</head>
<body>
<h1>Hello World!</h1>
<button type="button" onclick="myFunction()">Set background image to no-repeat</button>
<script>
function myFunction() {
document.body.style.backgroundRepeat = "no-repeat";
}
</script>
</body>
</html>