- Internet Explorer had a broken HTTP digest authentication before v7 and

there are servers "out there" that relies on the client doing this broken
  Digest authentication. Apache even comes with an option to work with such
  broken clients.

  The difference is only for URLs that contain a query-part (a '?'-letter and
  text to the right of it).

  libcurl now supports this quirk, and you enable it by setting the
  CURLAUTH_DIGEST_IE bit in the bitmask you pass to the CURLOPT_HTTPAUTH or
  CURLOPT_PROXYAUTH options. They are thus individually controlled to server
  and proxy.

docs/libcurl/curl_easy_setopt.3

@@ -21,7 +21,7 @@
 .\" * $Id$
 .\" **************************************************************************
 .\"
-.TH curl_easy_setopt 3 "28 Oct 2008" "libcurl 7.19.1" "libcurl Manual"
+.TH curl_easy_setopt 3 "11 Dec 2008" "libcurl 7.19.3" "libcurl Manual"
 .SH NAME
 curl_easy_setopt \- set options for a curl easy handle
 .SH SYNOPSIS
@@ -661,6 +661,13 @@ others.
 HTTP Digest authentication.  Digest authentication is defined in RFC2617 and
 is a more secure way to do authentication over public networks than the
 regular old-fashioned Basic method.
+.IP CURLAUTH_DIGEST_IE
+HTTP Digest authentication with an IE flavor.  Digest authentication is
+defined in RFC2617 and is a more secure way to do authentication over public
+networks than the regular old-fashioned Basic method. The IE flavor is simply
+that libcurl will use a special "quirk" that IE is known to have used before
+version 7 and that some servers require the client to use. (This define was
+added in 7.19.3)
 .IP CURLAUTH_GSSNEGOTIATE
 HTTP GSS-Negotiate authentication. The GSS-Negotiate (also known as plain
 \&"Negotiate") method was designed by Microsoft and is used in their web