Cannot delete Hosts on web interface

I had 2 servers on which I was doing tests and I don’t need these servers anymore.
When I am on the web interface, the “delete host” button is not available it is grayed out and I don’t understand why. Can someone help me?
Thank you for your understanding.

If the host is online the option is disabled. Removing an online host would cause errors and it would eventually get created again automatically. Once the host is offline it may take a minute for the host to be detected as offline.