<html>
<head>
<style>
body
{
background:#f3f3f3 url('img_tree.png') no-repeat fixed right top;
}
</style>
<script>
function bgAttachment()
{
var x=document.body.style.backgroundAttachment;
document.getElementById("toggle").innerHTML=(x=="scroll")? "Set bg image to scroll!":"Set bg image to fixed!";
document.body.style.backgroundAttachment=(x=="scroll")? "fixed":"scroll";
}
</script>
</head>
<body>
<button id="toggle" onclick="bgAttachment();">Set bg image to scroll</button>
<p>Scroll the page and watch the background image.</p>
<p>This is a paragraph</p>
<p>This is a paragraph</p>
<p>This is a paragraph</p>
<p>This is a paragraph</p>
<p>This is a paragraph</p>
<p>This is a paragraph</p>
<p>This is a paragraph</p>
<p>This is a paragraph</p>
<p>This is a paragraph</p>
<p>This is a paragraph</p>
<p>This is a paragraph</p>
<p>This is a paragraph</p>
<p>This is a paragraph</p>
<p>This is a paragraph</p>
</body>
</html>