Use cache manifest in wordpress themes
When the plugin activate, the plugin generated two files in your current theme\'s directory. These two files will be delete when plugin deactivate.
Just deactive and re-active the plugin.
Notes: your blog site served with the content type text/cache-manifest. If you are running an Apache-based web server, you can probably just put an AddType directive in the .htaccess file at the root of your web directory:
AddType text/cache-manifest .manifest