A TimThumb error has occured

The following error(s) occured:

The remote file is not a valid image. Mimetype = 'text/html' File = /var/www/html/timthumb/cache/timthumbrgLpUh

Query String : src=http://www.campeggio.it/foto/sistemazioni/piantina_b_0.gif&zc=1&h=70&w=100&a=c
TimThumb version : 2.8.13