How to block or unblock a website?

FOR BLOCKING Do The Following :

1. For example you want to block www.xyz.com !*
2. Open the folder C:\WINDOWS\system32\drivers\etc
3. There you will find a file named >> HOSTS
4. right click on it >> select open >> chosse Notepad >> ok
5. Now, in the file under the line 127.0.0.1 localhost add another line as 127.0.0.2 www.xyz.com
6. Now, File>>Save
7. For unblocking just follow the same procedure vice versa...!!!!!