HOW TO BLOCK WEBSITE IN YOUR SYSTEM

Go to my computer
open c:\ drive 

Go to Windows Folder 
open windows folder

go to system 32 folder
open system 32 folder

go to drivers folder
open drivers folder

look for a folder name etc and open the folder

their is a file name HOSTS 

open hosts file in notepad
go to last line and enter

their you type
127.0.0.1 (type your website that you would like to block)
Eg: 127.0.0.1 www.facebook.com