Always remember to include the mraid.js in the head section of the banner. It does not matter if the file is not present in the folder, it is just for detection purposes. Here is how it should look:
<head> <meta charset="UTF-8"> <script src="mraid.js"></script> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <meta name="HandheldFriendly" content="True" /> </head>
Do not use mraid.js in the body tag.
For full MRAID specifications please visit http://www.iab.net/mraid.