I need to block access to gmail and google+ on my children's mac books. I had no problem doing this before, however ever since I upgraded to Mountain Lion, I am stumped on how to do this. Please advise.....:
To save changes: control+o then control+m
To exit: control+x
Then run this to make the rules active.
sudo dscacheutil -flushcache
Now when someone tries to load plus.google.com, the system will check this file first, see that it needs to be redirected to 127.0.0.1 which is a loopback IP and error out because it can't find the server.