Block unwanted sites on a pc using notepad -Parental control

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There are many software in the market to block sites .But in every method You have to type  the websites which you want  to block in your computer.
                                                             Today i have a simple tut to do that  but i am not using any high weighted software which slows down my computer.We just need a notepad which is pre-built installed in every version of microsoft windows .