The NetCraft website provides statistical analysis services on other websites. NetCraft checks and reports on various sites’ operating systems and web server software (usually either Windows/IIS or Linux/Apache) which is useful during the reconnaissance stage of ethical hacking efforts.
For example, a NetCraft query for wordpress.com returns the following results:
IP address: 184.108.40.206
Domain Registrar: godaddy.com
Web Server: nginx
If you want to find out all of a particular website’s subdomains, you can use the search feature on the searchdns.netcraft.com page as shown below.