You can detect NGINX PHP FastCGI Default Test Page using this tool.
The remote web server uses its default welcome page. Therefore, it's probable that this server is not used at all or is serving content that is meant to be hidden.
The remote web server is not configured or is improperly configured. If attackers detect the test page, they will try to detect vulnerabilities related to this version of NGINX PHP FastCGI Server.
Disable this service if you do not use it or remove all test pages on your server.