I'm using Squid on OpenBSD.

I have some strange behauvor when blocking sites,

the problem is when you tipe something into a text box and ask for the reply, for ex. when you send a search in google.

www.google.com it's opened ok but if a do a search, the next page cannot be displayed because a deny action.

No only google, just all pages that have forms do.

For blocking sites i add an
act something url_regex "file"

and then a
http_access deny something


the file has a list with url's, witch are succesfully access denied.

If i comment those files, google, yahoo, and all forms works ok.

What format are the urls in the file, you must ensure that the url is converted to a regaular expression. E.g. the url

http://www.google.co.uk

should be listed in the file as

http://www\.google\.co\.uk

You should escape the dots as they mean any char. Without knowing what you have in the file its hard to say what would match