Since you don’t want kids to accidentally see any of sites that contain adult content, an easy option for blocking such sites is OpenDNS.
You don’t have to download or install any software - just go to opendns.com/start in any Internet browser, choose the "Computer" option (let’s keep it simple) and follow the instructions on the screen. Once your computer is configured with OpenDNS, go to Dashboard -> Settings and set the Filtering level to either Moderate or High.
Now whenever your kid mistakenly types a URL of some adult site in the browser (e.g. whitehouse.com instead of whitehouse.gov) or clicks a link that may be pointing to an inappropriate site, the OpenDNS filters will match the address of that site against their own database of adults sites and if there’s a match, the underlying web page won’t be displayed on the child’s computer.
Source : Digital Inspiration
