How to Block Access to YouTube
Youtube is a popular online video sharing site where you can upload videos that you have created to share with the world. If you want to block access to Youtube for security or other reasons, you can do so by altering the hosts file on your computer. The hosts file is one that your computer looks at for redirect information and you can use it to redirect all requests for Youtube back to your own computer, blocking off access to the website.
Open the Start menu on your computer, type "notepad" in the search box, right-click on the "Notepad" application and click "Run as administrator."
Click "OK" or "Yes" to start Notepad as the administrator, click "File," then "Open" in Notepad.
Open the "C:\System32\drivers\etc\hosts" file.
Add the following line, without quotes, to the end of the hosts file: "127.0.0.1 youtube.com"
Save the file in Notepad and Youtube is blocked.