A TimThumb error has occured

The following error(s) occured:

You may not fetch images from that site. To enable this site in timthumb, you can either add it to $ALLOWED_SITES and set ALLOW_EXTERNAL=true. Or you can set ALLOW_ALL_EXTERNAL_SITES=true, depending on your security needs.

Query String : src=http://goindiebooks.com/408847/wp-content/uploads/2013/05/slide1.png&w=960&h=500&zc=1
TimThumb version : 2.8.10