The simple check for http only check if the port is open. You should remove http from the supported services, as it is really misleading,
or implement a real check. It should do a GET for '/' , and validate that

• the answer comes from a web server (HTTP...)
• and that the answer is OK (in the range 2xx or 3xx) .

For my implementation, web scenarios are too heavywheight and not enougth integrated with the templating system to be useful.