HTTP Status Code 505 signifies HTTP Version Not Supported, which means that the server does not support the HTTP protocol version that was used in the request. This status code indicates that the client has requested an HTTP version that the server cannot handle, and thus it cannot fulfill the request. When a server responds with HTTP Status Code 505, it suggests that the client should consider using a different version of HTTP that is compatible with the server. In practice, this often occurs when there is a mismatch between the versions of HTTP supported by the client and the server, highlighting the importance of adhering to standard protocol versions during communication.