You can adjust the ACL to fit that requirement. Deny the specified host first, then allow all others.
access-list testacl extended deny tcp host 192.168.121.11 host a.b.c.d eq 80
access-list testacl extended permit tcp host 192.168.121.11 any eq 80
Unfortunatly Cisco can not filter on a domain name in an ACL, so you must use the IP. You may have to block more than IP to block the site. You can block it by domain name if you use the Modular Policy Framework. If that is something you're interested in, just let us know.