\.sex\.com
\.redtube\.com
I also recommend you to block this way to cover all the possibilities:
^http://.*\.*sex\.com/*.*
^http://.*\.*redtube\.com/*.*
Let me explain what are you telling to squid to do with this regex:
^ = this is the beginning of the url
http:// = is the protocol that is always required
. = anything, for example, can be a subdomain or a www
* = the expression BEFORE (the subdomain or www) can happen or not
\ = the next char is not "anything" but a real dot
. = the real dot...
* = ...that can happen or not
sex = the domain
. = next char is a real real dot again
com = top level domain
/* = a dash that can happen or not (covering all the possible websites configurations here)
.* = anything can happen or not after the last dash (/index.php, blah blah)
