HTTP response status codes indicate whether a specific HTTP request has been successfully completed. Responses are grouped in five classes: Informational responses (100–199) Successful responses (200–299) Redirects (300–399) Client errors (400–499) Server errors (500–599)

1. HTTP Status
Code
Analysis of Status Code of
Client error response 416 vs 428 and
Server error response 503 vs 505

2. HTTP Status Codes
416: Range Not Satisfied
428: Precondition Required
503: Service Unavailable
505: HTTP Version
Not Supported

3. 416: Range Not Satisfied
Range Not Satisfiable error response code indicates that a
server cannot serve the requested ranges.
The most likely reason is that the document doesn't contain
such ranges, or that the Range header value, though
syntactically correct, doesn't make sense.

4. •428: Precondition Required
Precondition Required response status code indicates that the
server requires the request to be conditional.
Typically, this means that a required precondition header, such
as If-Match, is missing.
When a precondition header is not matching the server side
state, the response should be 412 Precondition Failed.

5. 503: Service Unavailable
Service Unavailable server error response code indicates that
the server is not ready to handle the request.
Common causes are a server that is down for maintenance or
that is overloaded. This response should be used for temporary
conditions and the Retry-After HTTP header should, if
possible, contain the estimated time for the recovery of the
service.

6. 503: Service Unavailable
Why this occurs:
 Service is unavailable for maintenance
 To many request so that server cannot work properly
 The servers content move permanently

7. 503: Service Unavailable
How to fix error:
 Refresh the page
 See if the page is down for other people
 Restart your router.
 Restart the server.
 Check the server logs.
 Check if there's ongoing automated maintenance.
 Check your server's firewall settings.
 Check the code

8. 505: HTTP Version Not Supported
HTTP Version Not Supported response status code indicates
that the HTTP version used in the request is not supported by
the server.

9. 505: HTTP Version Not Supported
How to fix error:
 Try to upgrade HTTP version
 Reinstall browser
 Switch to modern browser