I haven't seen any posts on this so I thought I'd give this a shot.
Have you ever had someone come over and they get on site you don't like? Or just play with someone.
This will make any website you put non-accessible until you make in accessible again.
1. Go to "My computer" or "computer"
2. Get on you're local disk.
3. Open up you're "windows" folder.
4. Head to "system32"
5. Then go to "Drivers"
6. When you are there, find "ect"
7. Once you are there open up Notepad.
Drag the file that says "host" into note pad.