Best way to Block Accessing given URL’s in Windows

Go To directory
C:\Windows\System32\drivers\etc
open hosts file in notepad and add following text and save it.make sure you are the admin of the system else you may not be able to modify this file.site name and domain select as you need.in this case what windows system does is send request with the given site name to to the network address that we provided.since 127 is private ip range it does not redirect to any web site on internet.so this will shows server not found message.

127.0.0.1 www.sitename.com