There are commercially available softwares which will prevent access to websites you specify from your computer. But this can also be done on your computer without even spending a single penny. We will show you how to do it absolutely for free:
1. Browse to C:\WINDOWS\system32\drivers\etc
2. Find the file named hosts (for linux users, this file is locate in the /etc/ directory. you could run a sudo nano /etc/hosts/ to edit the file)
3. Open it in notepad.
4. Under the line that says 127.0.0.1 localhost Add a new entry 127.0.0.2 <website to be blocked> and save the file.
5. The website will no longer be accessible. (you might be required to restart your computer.)
For every site after that you want to be blocked, just add "1" to the last number in the internal ip (127.0.0.2) followed by the web address to be blocked, as shown below:
127.0.0.33 website33 .... and so on.
Related Article: How-To get the real ip address of a visitor on your website?