1. Login to Blogger> Open Template editor> Add the code below before ]]> </ b: skin> or </ style>
#cssload {background:url(https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjvVCUw7zDVXM-gVFZAhb3OIKzfHDc9le6fDC5xd7o-P0VY3-nRYRpwjUjAxAHIAMyUdhStZTVAMO8fafSh5h9OELuqI1L-jfQrv1foP7pfm35UBcFv7cYWhKWcAlSHVnV_QBj9OM2pKfrS/h120/loader.gif) no-repeat center;background-color:rgba(0,0,0,0.36);width:100%;height:100%;position:fixed;left:0;top:0;z-index:1000;}
2. Then add the following code under the <body>
<div id='cssload'/>
3. Add the following code before the </ body>
<script type='text/javascript'>
//<![CDATA[
// Loader
$(window).bind("load",function(){$("#cssload").fadeOut(1e3)});
//]]>
</script>
4. Save the template and see the results.