function changeBackground() {
	$('pwd').setStyle("background:url('images/password.jpg') no-repeat;");
	$('pwd').observe("focus", function(event) {
		field = Event.element(event);
		event.stop();
		field.setStyle("background:#fff;");
	});
	
	$('pwd').observe("blur", function(event) {
		field = Event.element(event);
		event.stop();
		if(!field.getValue()) {
			field.setStyle("background:url('images/password.jpg') no-repeat;");
		}
	});
}

document.observe("dom:loaded", changeBackground);