This has many solutions, but a simple one is to:
1- Create an overlay DIV with your loader stuff and prepend to BODY;
2- Add an event listener for window.load
or document.ready
event that hides this DIV.
// On the first line inside BODY tag <script type="text/javascript"> jQuery("body").prepend('<div id="preloader">Loading...</div>'); jQuery(document).ready(function() { jQuery("#preloader").remove(); }); </script>
(code typos fixed)