<script type="text/javascript" src="/js/jquery.js"></script>
<script type="text/javascript">
$(document).ready(function(){
$(".btn1").click(function(){
$("body").animate({backgroundPosition:"40% 40%"},0);
$(".btn2").click(function(){
$("body").animate({backgroundPosition:"0% 0%"},0);
<body style="background-image:url(/img/eg_background.jpg);background-repeat:no-repeat;background-attachment:fixed;">
<p>This is a paragraph.</p>
<button class="btn1">Animate</button>
<button class="btn2">Reset</button>