Doc-info is a Perl script which gathers together and returns to the user information pertaining to the document from which it was activated. It identifies the document for which information is being sought by looking at the value of the environment variable 'HTTP_REFERER'.
In this case, 'HTTP_REFERER' was unset. Perhaps your browser simply doesn't set this variable. More likely, this script was requested not in a document context; i.e., the URL was requested directly. Robots (web wanderers) do this occasionally.
In any event, without this datum doc-info cannot supply you with the requested information. If you feel you have received this in error, or still want the information, please contact roth@cs.uaf.edu. Be sure to supply the URL of the document for which you wish information, if that's what you want.