Actually, HOSTS file is using by Windows to mapping host name to an IP address. Windows has been giving us a sample. The sample is localhost name, by default that host name is mapping to IP address: 127.0.0.1. So, if you enter localhost at your browser address bar, Windows will map localhost to 127.0.0.1 address. And you can add your own host name to your chosen IP address.

So, look its feature, we can block a website or many websites addresses. Just simple, map your ‘hated’ website address to 127.0.0.1 address. As you know, 127.0.0.1 is localhost address, so if you map adxxx.com to 127.0.0.1, Windows will access 127.0.0.1 every your access adxxx.com. And here are the steps:
1. Open folder: C:\Windows\System32\drivers\etc. C:\Windows is your Windows installation folder and you may change it if your Windows folder is different with mine. Or you can enter in Run box %systemroot%\system32\drivers\etc and then press Enter.

2. Then find hosts file, open that file by double click it. If it is not associate yet with text editor, Open With window will appear and then choose Notepad as default application.

3. After hosts file is opened, you’ll see its description and localhost mapping.

4. To create new map address, just add to new line and map it to 127.0.0.1 host_name. For example, if you want block domain name: typeyourdomainhere.com, just write at new line, 127.0.0.1 typeyourdomainhere.com and then save it by press Ctrl + S keys or click File –> Save menu.

5. Now, try access your blocked website address.

Then, just add other addresses to block the naughty website.