<html>
<head>
<script language="JavaScript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.5.0/jquery.min.js"></script>
<style>
div {
width: 200px;
height: 100px;
border: 1px solid;
background: url('http://javascript.ru/forum/images/smilies/smile.gif') no-repeat;
background-position: 0 0;
}
</style>
<script>
function Go() {
$("#box").css({backgroundPosition: '10px 20px'});
}
</script>
</head>
<body>
<div id='box'></div>
<input type='button' value='Go' onclick='Go()' />
</body>
</html>
Вот на JQuery