Our team at Red Hat maintains a couple of internally facing services (called ODCS and CTS). Not everyone is familiar with the fact that these services run in the back-end. Sometimes people would visit the URL in their browser and wouldn’t be able to load any page. Then they would report particular service isn’t working.
This is why simple HTML page was created for each service to serve as a front-end. Content-wise it’s a very basic page with only the name, description and links. Originally, design-wise only a raw HTML was used without any CSS.