Blocking a site using these steps will only block the website on one computer. Any other computer, phone, or tablet connected to your computer will be able to access the site you're blocking.

A website can be blocked on any Windows computer by editing the hosts file, in Windows this file is referred to as the lmhost file.

Locate the hosts file in Windows Explorer. For Windows XP and up, it will be located in the directory C:\WINDOWS\system32\drivers\etc\. In Windows 2000/NT, C:\WINNT\system32\drivers\etc\. In Windows 98 and ME, C:\WINDOWS\system32\drivers\etc\. In windows 7 and 8.

Navigate to the proper directory using Windows Explorer. Double-click the hosts file. Choose Notepad from the list of programs to open the file and edit it in Notepad.

Find the line below:

Right underneath it, add the following lines (replacing Mywebsite.com with the site you wish to block):

 NOTE:- Now u want to save this file but it will never save. So don't panic. Now Right click on the host  file. Go on the Security tap. Now click on the EDIT. Then click on the Full Control. then Apply and Ok.

Click on the File menu and click Save. Close the file. The site should be blocked in all web browsers and now instead of trying to access that site the computer will redirect you to the localhost.