A small defun you may find useful:
(defun open-mozilla-extension-urn () "Open the extension directory for the first extension urn on the current line. Uses the directory the buffer \"Extensions.rdf\" is in as a base. urn's look like: \"urn:mozilla:extension:\"." (interactive) (let ((l (thing-at-point 'line))) (if (string-match "\"urn:mozilla:extension:\\(.+\\)\"" l) (find-file (concat (file-name-directory (buffer-file-name (get-buffer "Extensions.rdf"))) (match-string 1 l))))))
Written by JesseWeinstein; released to public domain on Wed May 25 16:51:09 2005.