If you want to Block unwanted sites there is a method to follow take a look how to do it.However this requires bit of editing of hosts file in the windows directory.
1.Click Start,Run and Type cmd this will open command Prompt window and type cd\ to get to C Directory.
2.Now type notepad C:/Windows/System32/drivers/etc/hosts
and press Enter
3.This open hosts file in a notepad,now locate the file 127.0.0.1 localhost and add the text of the site you want to block like www.saicomputers.tk under it.127.0.0.1 should be before that site
4.Save the file and Open the Browser and see if Blocked site is opening or not.
5.Now if you want to unblock that site again do the same procedure open the hosts file from cmd and remove the line we have added .