Kozierok in The TCP/IP Guide (pg.1363):
The proper spelling of this word is referrer. It was misspelled years ago in an earlier version of the HTTP standard, and before this was noticed and corrected, this spelling became incorporated into so much software that the Internet Engineering Task Force (IETF) chose not to correct the spelling in HTTP/1.1.
Phillip Hallam-Baker on his choice of spelling:
Its like when I did the referer field. I got nothing but grief for my choice of spelling. I am now attempting to get the spelling corrected in the OED since my spelling is used several billion times a minute more than theirs.
Apparently, neither referer nor referrer was included in the spell checker dictionary:
From: Roy T. Fielding <fielding@avron.ICS.UCI.EDU> Date: Thu, 09 Mar 1995 21:24:23 -0800 To: John Franks <email@example.com> Cc: firstname.lastname@example.org Message-Id: <email@example.com> > Has anyone else noticed that the HTTP header "Referer:" is spelled wrong? That's okay, neither one (referer or referrer) is understood by "spell" anyway. I say we should just blame it on France. ;-) ........Roy