How to Block Unwanted Website in Ubuntu Linux?

The process to block websites in Ubuntu Linux is very simple and doesn't
require any third party application. You just need to make a simple
entry in the /etc/hosts file. /etc/hosts is a very important file which
handles DNS and internet handling on Linux based systems. In order to
block some site from opening, open the /etc/hosts file by typing the
following command on the terminal:

gedit /etc/hosts

and add the following line:

127.0.0.1 domain.com

Example 127.0.0.1 yahoo.com

Here replace domain.com with the name of the domain that you wish to
block. Once the above exercise is done, who ever tries to access the
site will get a message "Failed to Connect".