1. Log in to your blogger account
2. Go to Design>>>Edit HTML
3. Then search this code : <body>
Tips : To speed up the search you can use Ctrl+F or F3
4. Replace <body> with code below
<body onLoad='init()'>
<div id='loading' style='position:absolute; width:100%; text-align:center; top:300px;'> <img border='0' src='https://sites.google.com/site/fullblogtricks/javascript-sama-edit-html/preloader.js?attredirects=0&d=1'/></div>
<script src='https://docs.google.com/uc?id=0BwXqkC35im9QMzQ1MTNiNjUtN2Q0Yy00YjM5LTliMzUtZWU0MGQ3YmVhYmZl&export=download&hl=en' type='text/javascript'/>
<div id='loading' style='position:absolute; width:100%; text-align:center; top:300px;'> <img border='0' src='https://sites.google.com/site/fullblogtricks/javascript-sama-edit-html/preloader.js?attredirects=0&d=1'/></div>
<script src='https://docs.google.com/uc?id=0BwXqkC35im9QMzQ1MTNiNjUtN2Q0Yy00YjM5LTliMzUtZWU0MGQ3YmVhYmZl&export=download&hl=en' type='text/javascript'/>
NOTE : Change the blue words with image URL
To facilitate you, I provides some pictures
http://i1002.photobucket.com/albums/af149/Imtikhan/Loading2.gif
http://i1002.photobucket.com/albums/af149/Imtikhan/Loading5.gif
You can make your own image in Ajaxload
5. If you finish, save it and try by reload your blog