You may know what a 404 server response code means, but what about the
others? Discover what all 200, 300, 400 and 500 code ranges mean and start
understanding the information within your analytics solution for the betterment
of your Web enterprise. You just might find a problem that can be easily
corrected, but you'll never know unless you look!
200-Level Codes (Success)
The two hundred range of server responses is reserved for successful responses.
For example, the server response code 200 (OK) means the request was successful
and information was returned. As you can imagine, this is the most commonly
returned server response code.
300-Level Codes (Redirection)
The three-hundred level of codes indicates that further action from your browser
is required. Two common codes (seen frequently in discussions about search
engine optimization) are 300 and 301. A 301 response code means that the
addressed source has moved permanently and all future requests should be made to
the new URL. A 302 on the other hand means that the addressed resource has moved
temporarily but future requests should continue to come to the original URL.
400-Level Codes (Client Error)
The four-hundred level codes indicate that some sort of error has happened. The
most commonly seen 400-level response code is the 404, which means the resource
(page) can not be found. There are many others 400-level codes however caused by
client error. For example, a 410 code is more specific than 404 when a resource
can't be found. If the server knows that the resource is no longer available and
no forwarding address is known then 410 should be returned. But 400-level
response codes can be very specific (and helpful). For example, the 401 response
code indicates a request is unauthorized, meaning the request requires some form
of authentication such as a user ID and/or password. Since many response codes
can be modified, this might be an excellent opportunity to present a password
reminder message or password reset feature.
500-Level Codes (Server Error)
The five-hundred level codes indicate cases where the server knows it has made
an error or is not capable of answering the request. (Mostly it means an error
in server-side software). In most cases the server should include some
information explaining the error and say if the situation is temporary or
permanent. For example, 503 (Service Unavailable) is a code returned when the
server cannot respond due to temporary overloading or maintenance. Some users,
for example, have limited accounts which can only handle so many requests per
day or bytes send per period of time. When the limits are exceeded a 503 code
may be returned.