If you want to block and unblock websites then I have a trick to do it without using any software.so follow these steps and do what you want with a particular websites:
To block a website
1. Click start Button then click “Run"
2. Type the following command in the “run” then press “ok”
3. A pop up window of notepad will open
4. Suppose you want to block the website facebook.com then add
127.0.0.1 facebook.com as shown in pic below
5. Now press CTRL+S to save the file.
6. Restart the internet browser.
In this way you have blocked facebook.com on your computer. Replace it with any website address and you will be able to block that website.
To unblock a website
1. Repeat from step 1 to step 3 as mentioned above.
2. Now delete 127.0.0.1 facebook.com from pop up window of notepad.
3. Now press CTRL+S to save the file.
4. Restart the internet browser.
Now you have unblocked facebook.com on your computer.