LogFormat directive
Default: LogFormat "%h %l %u %t \"%r\" %>s %b"

The characteristics of the request itself are logged by placing
"%" directives in the format string, which are replaced in the log file
by the values as follows:
%...a:          Remote IP-address
%...A:          Local IP-address
%...B:          Bytes sent, excluding HTTP headers.
%...b:          Bytes sent, excluding HTTP headers. In CLF format
i.e. a '-' rather than a 0 when no bytes are sent.
%...c:          Connection status when response is completed.
                'X' = connection aborted before the response completed.
                '+' = connection may be kept alive after the response is sent.
                '-' = connection will be closed after the response is sent.
%...{FOOBAR}e:  The contents of the environment variable FOOBAR
%...f:          Filename
%...h:          Remote host
%...HThe request protocol
%...{Foobar}i:  The contents of Foobar: header line(s) in the request
                sent to the server.
%...l:          Remote logname (from identd, if supplied)
%...mThe request method
%...{Foobar}n:  The contents of note "Foobar" from another module.
%...{Foobar}o:  The contents of Foobar: header line(s) in the reply.
%...p:          The canonical Port of the server serving the request
%...P:          The process ID of the child that serviced the request.
%...qThe query string (prepended with a ? if a query string exists,
otherwise an empty string)
%...r:          First line of request
%...s:          Status.  For requests that got internally redirected, this is
                the status of the *original* request --- %...>s for the last.
%...t:          Time, in common log format time format (standard english 
format)
%...{format}t:  The time, in the form given by format, which should
                be in strftime(3) format. (potentially localized)
%...T:          The time taken to serve the request, in seconds.
%...u:          Remote user (from auth; may be bogus if return status (%s) is 
401)
%...U:          The URL path requested.
%...v:          The canonical ServerName of the server serving the request.
%...V:          The server name according to the UseCanonicalName setting.

* apache.HTTP_ERROR, meaning an HTTP error occurred. HTTP_ERROR can be:

HTTP_CONTINUE                     = 100
HTTP_SWITCHING_PROTOCOLS          = 101
HTTP_PROCESSING                   = 102
HTTP_OK                           = 200
HTTP_CREATED                      = 201
HTTP_ACCEPTED                     = 202
HTTP_NON_AUTHORITATIVE            = 203
HTTP_NO_CONTENT                   = 204
HTTP_RESET_CONTENT                = 205
HTTP_PARTIAL_CONTENT              = 206
HTTP_MULTI_STATUS                 = 207
HTTP_MULTIPLE_CHOICES             = 300
HTTP_MOVED_PERMANENTLY            = 301
HTTP_MOVED_TEMPORARILY            = 302
HTTP_SEE_OTHER                    = 303
HTTP_NOT_MODIFIED                 = 304
HTTP_USE_PROXY                    = 305
HTTP_TEMPORARY_REDIRECT           = 307
HTTP_BAD_REQUEST                  = 400
HTTP_UNAUTHORIZED                 = 401
HTTP_PAYMENT_REQUIRED             = 402
HTTP_FORBIDDEN                    = 403
HTTP_NOT_FOUND                    = 404
HTTP_METHOD_NOT_ALLOWED           = 405
HTTP_NOT_ACCEPTABLE               = 406
HTTP_PROXY_AUTHENTICATION_REQUIRED= 407
HTTP_REQUEST_TIME_OUT             = 408
HTTP_CONFLICT                     = 409
HTTP_GONE                         = 410
HTTP_LENGTH_REQUIRED              = 411
HTTP_PRECONDITION_FAILED          = 412
HTTP_REQUEST_ENTITY_TOO_LARGE     = 413
HTTP_REQUEST_URI_TOO_LARGE        = 414
HTTP_UNSUPPORTED_MEDIA_TYPE       = 415
HTTP_RANGE_NOT_SATISFIABLE        = 416
HTTP_EXPECTATION_FAILED           = 417
HTTP_UNPROCESSABLE_ENTITY         = 422
HTTP_LOCKED                       = 423
HTTP_FAILED_DEPENDENCY            = 424
HTTP_INTERNAL_SERVER_ERROR        = 500
HTTP_NOT_IMPLEMENTED              = 501
HTTP_BAD_GATEWAY                  = 502
HTTP_SERVICE_UNAVAILABLE          = 503
HTTP_GATEWAY_TIME_OUT             = 504
HTTP_VERSION_NOT_SUPPORTED        = 505
HTTP_VARIANT_ALSO_VARIES          = 506
HTTP_INSUFFICIENT_STORAGE         = 507
HTTP_NOT_EXTENDED                 = 510