If you want a quick way to test if your DNS filtering is working try accessing www.internetbadguys.com
If this site is being blocked properly you should see something like the following;
Remember that you can get this security filtering for free. Simply point your DNS to 188.8.131.52 and 184.108.40.206.
Cisco Cloud Web Security (CWS) and OpenDNS both provide cloud based security services. CWS offers an HTTP/HTTPS proxy and OpenDNS provides security and visibility at the DNS resolution layer. I’ve been asked many times where both CWS and OpenDNS host their services as this can make a big impact in end user experience if the hosting location is far away from the user and could lead to high latency and a lousy experience.
CWS Proxy Location and Status Page: http://servicestatus.sco.cisco.com/status
OpenDNS Location and Status Page: https://www.opendns.com/data-center-locations/