<html>
<head>
<style type="text/css">
body
{
background:#f3f3f3 url('img_tree.png');
}
</style>
<script>
function displayResult()
{
document.body.style.backgroundRepeat="repeat-y";
}
</script>
</head>
<body>
<button type="button" onclick="displayResult()">Repeat background image only vertically</button>
<br>
<h1>Hello World!</h1>
<p>This is a paragraph</p>
</body>
</html>