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The link checker should do a GET request when the server replies 501 to a HEAD request.
JFTR, some servers don't send 501 if they don't like HEAD, e.g. http://www.rsasecurity.com/rsalabs/challenges/factoring/numbers.html Trying to write my own checklink (REXX + rxsock.dll on OS/2) I obviously caused some serious trouble for some servers. My new strategy is to never test any given host again if it sent 400, 405, or 5??. Until now I haven't seen any 501, and if I understand RfC 2916 correctly 501 *_should not_* be used in replies to HEAD requests.
You're right, the results with servers that do not support HEAD vary a lot, almost any status can be the result. For example as reported in http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=188123 But RFC's 1945, 2068 and 2616 (section 5.1.1) all mention 501 as a "SHOULD" for unrecognized methods; 2068 and 2616 additionally define the possibility of a 405. I have always though that support for HEAD is a "MUST" in HTTP 1.1, but RFC 2616 (and 2068, FWIW) say: "The methods GET and HEAD MUST be supported by all general-purpose servers." Note "general-purpose". *sigh*
Oops... tnx for this "general purpose" hint. That's a bit like the many lines explaining GMT in date-headers, and ending with the conclusion, that a server can omit this header if it has difficulties to determine Zulu time... ;-) Actually this makes sense (routers without clock etc.), but not supporting HEAD is hard. Better stay away from GET, at least as long as you don't support robots.txt BTW, do you have admin rights on this bugzilla ? If YES please (re)enable the option to modify mail addresses. It exists, I've seen it on the distributed bugzilla, where I could change my address.
I haven't seen the option to change a mail address in any Bugzilla. Not to say such a thing doesn't exist, but I believe it's a recent addition, most likely available in newer versions than this one. And no, my rights aren't up to the task anyway, I suggest contacting Terje Bless <link@pobox.com> and/or Olivier Thereaux <ot@w3.org> on Bugzilla issues, I believe they have the necessary admin rights. Hm, maybe a component named "Bugzilla" wouldn't be a bad idea here... :)