[DOC] document HTTP status codes
diff --git a/doc/configuration.txt b/doc/configuration.txt
index b4b3596..704b97c 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -515,6 +515,29 @@
messages. It can be composed of one or multiple words, such as "OK", "Found",
or "Authentication Required".
+Haproxy may emit the following status codes by itself :
+
+ Code When / reason
+ 200 access to stats page, and when replying to monitoring requests
+ 301 when performing a redirection, depending on the configured code
+ 302 when performing a redirection, depending on the configured code
+ 303 when performing a redirection, depending on the configured code
+ 400 for an invalid or too large request
+ 401 when an authentication is required to perform the action (when
+ accessing the stats page)
+ 403 when a request is forbidden by a "block" ACL or "reqdeny" filter
+ 408 when the request timeout strikes before the request is complete
+ 500 when haproxy encounters an unrecoverable internal error, such as a
+ memory allocation failure, which should never happen
+ 502 when the server returns an empty, invalid or incomplete response, or
+ when an "rspdeny" filter blocks the response.
+ 503 when no server was available to handle the request, or in response to
+ monitoring requests which match the "monitor fail" condition
+ 504 when the response timeout strikes before the server responds
+
+The error 4xx and 5xx codes above may be customized (see "errorloc" in section
+2.2).
+
2.1.3.2) The response headers
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