I am no expert, but I did read the Tutorial at
http://iptables-tutorial.frozentux.n...-tutorial.html recently.
(reference table 6.4 on this page)
It appears to me you could use CIDR format only. I'm thinking you could resolve the URL to an IP or IP range if it has mutiple host
then block it that way. I didn't see anything about blocking a URL though. (eg...192.168.0.1/24)
If anyone else knows another way I'd be curious to know myself.