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://www.asu.cas.cz/_data/Pozvanka_Brno_1311181493.jpg&w=70&h=65&zc=1
TimThumb version : 2.8