This group means that the request is received and has been understood. As the HTTP/1.0 standard did not define any 1xx status code, servers must not send a 1xx response to an HTTP/1.0 compliant client except under experimental conditions.
This class of codes indicates that the clients request was received, understood and accepted.
Next is . This class of status code indicates that the client should take additional action to complete the request. Many of these status codes are used in URL redirection.
A user agent may carry out the additional action with no user interaction only if the method used in the second request is GET or HEAD. A user agent may automatically redirect a request. A user agent should detect and intervene to prevent cyclical redirects.
This kind of status code point out the situations in which the error seems has been caused by the client. Except when responding to a HEAD request, the server should include an entity containing an explanation of the error situation, and whether it is a temporary or permanent condition. These status codes are applicable for any request method. User agents should display any included entity to the user.
And finally . The 5xx group includes the cases when the server failed to accomplish a request. It means that the server is aware that it has encountered an error or is otherwise incapable of performing the request. Except when responding to a HEAD request, the server should include an entity containing an explanation of the error situation, and show whether it is a temporary or permanent condition. Here are all status code classes. Now let’s see which ones are the most commons. If you want see all list of status codes you can check this.
it means your request is successfully done.
304 not modified:
it reports that the resource has not been changed from the version specified by the If-Modified-Since or If-None-Match request headers. In this case, there is no need to re-transmit the resource, because the client still has a previously downloaded copy.
400 bad request:
The server cannot or will not process the request because of an obvious client error, for example malformed request syntax, size too large, invalid request message framing.
401 semantically means "unauthenticated", i.e. the user does not have the necessary credentials. Similar to 403 Forbidden, but specifically for use when authentication is required and has failed or has not yet been provided.
The request was valid, but the server is refusing action. The user might not have the necessary permissions for a resource, or may need an account of some sort.
404 not found:
The requested resource can not be found, but may be available in the future. possibly, requested by the client.
Indicates that the request could not be processed because of conflict in the request, such as an edit conflict between multiple simultaneous updates.
500 internal server error:
A generic error message, given when an unexpected condition was encountered and no more specific message is suitable.
That is all!