<style>
.loading{
background: url(http://www.ajaxload.info/images/indicator.gif);
position: absolute;
top: 50%;
left: 50%;
margin-top: -16px;
margin-left: -16px;
width: 32px;
height: 32px;
}
</style>
<body>
<script>
var loading = document.createElement('div');
loading.className = 'loading';
document.body.appendChild(loading);
setTimeout(function() {
loading.parentNode.removeChild(loading);
}, 3000);
</script>
</body>