Some persons appear to be offended by people posting to threads that have had no activity in a long time. They refer to these threads by various phrases and catch words including "necro" (or compounds of it) which is derived from a Latin term meaning "dead". An example of the original meaning would be in "necropolis", meaning "city of the dead" or as we would now say "cemetery". Myself, I see no problem with posting to an old thread, if that seems appropriate, although the occasionally seen advice to someone who has posted nothing further for a few years does seem rather pointless.