Someone

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title></title>
<script type="text/javascript">
function change(){
var p = document.getElementById('price'); 
	while(p.firstChild){
	 p.removeChild(p.firstChild);
	} 
	p.appendChild(document.createTextNode('free'));
}
</script>
</head>
<body>
<div class="price" id="price" onclick="change()"> $10 </div>
</body>
</html>