Re: error produced with cl-http by latest Mozilla browsers

Consult the HTTP 1.1 specification: http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html

You will need to verify that http 1.0 clients behave as expected, and report back if
there are issues.

The patch below corrects CL-HTTP to use 303 for redirects within a POST response.

;; Use the forward condition for all redirects within a post method per HTTP 1.1 spec
;; http:server;report.lisp
(defun %standard-url-redirect (url target-url redirection-type method target-window)
  (check-type target-window (or null string))
  (let ((alternate-urls (ensure-list target-url)))
    (unless alternate-urls
      (signal 'document-not-found :url url))
    (case method
      (:post (signal 'document-forwarded :url url :method method :new-urls alternate-urls :target-window target-window))
      (t (ecase redirection-type
           (:temporary-redirect
            (case method
              (:get (signal 'document-found :url url :method method :new-urls alternate-urls :target-window target-window))
              (t (signal 'document-moved-temporarily :url url :method method :new-urls alternate-urls :target-window target-window))))
           (:permanent-redirect
            (signal 'document-moved-permanently :url url :method method :new-urls alternate-urls :target-window target-window))
           (:forward
            (if (and (eql method :get) (not (explicit-expiration-p url)))
                (signal 'document-forwarded :url url :method method :new-urls alternate-urls :target-window target-window)
              (signal 'document-moved-temporarily :url url :method method :new-urls alternate-urls :target-window target-window)))
           (:proxy
            (signal 'document-access-via-proxy :url url :method method :new-urls alternate-urls :target-window target-window))
           (:multiple-choices
            (signal 'document-multiple-choices :url url :method method :new-urls alternate-urls :target-window target-window)))))))

I tested the patch on Mozilla 1.6 and Safari running under Mac OS X 10.3.4

This will be incorporated into the next release.

Good test case. Thanks for Martin's comment.

This is a rather interesting example of the high-level abstraction in CL-HTTP, where a small change here implements
the desired functionality without forcing the application to know what is going on below. Note also that 

(report-status-line (condition http/1.1-redirection-downgrade-mixin) (stream t))

automatically conditionalizes the output for http  1.0 clients.