I have some troubles with my Squid config. For exmple I want to block the entire domain "facebook.com", but when I ad it to my ACL-file I still can access for example "new.facebook.com" and all other subdomains in that domain.

I have also tried to block for example:

.facebook.com
*facebook.com
*.facebook.com

But nothing works. The only way to block domain and subdomains in my case is to block each subdomain itself, and that is to much work for every site I'd like to block.

I solved this by adding a block of URL contents with url_regex, so if the word "facebook.com" is in the URL, then the site is blocked. But I don't think this is a good solution.

Do someone know a good solution for this?

That's what I was going to suggest. Why is it not a good solution? You could specify a more specific regular expression if you're worried about blocking false positives.

It didn't feel like a proper solution when the manual said that it should be possible to block a whole domain instead of words in the URL.

But somehow I solved it. Before it didn't work to ban for example .facebook.com. But when I tried again it works fine. Wierd but now it works.