OpenDNS and Google Public DNS are free, global Domain Name System (DNS) resolution services, that you can use as an alternative to your current DNS provider.
In my case : Wired > Edit > IP4 Settings
At Method open the dropdown menu and select Automatic (DHCP) addresses only.
In the DNS servers field, enter the following IP addresses, separated by a comma.
For OpenDNS : 18.104.22.168, 22.214.171.124
For Google Public DNS : 126.96.36.199, 188.8.131.52
Restart Networkmanager ( might not be needed ) :
sudo service network-manager restart
Restart your browser...
To check run the next command in a Terminal :
nm-tool | tail -n 8
OpenDNS checker : http://welcome.opendns.com/