I have your answer!
Go to Control Panel, Network and Internet, Network and Sharing Centre, Local Area Connection, Properties, Double click Internet Protocol Version 4, click box use following DNS server address, In prefered DNS Server put 208.67.222.123
Now in the Alternate DNS Server put 208.67.220.123 and then click OK
Now search in google the word sex for example, click on a site and you will notice it is blocked to go on.
Hope this helps
This is all based on Windows 7 by the way, not sure about others, you can do it, but I cant remember in detail like this.
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