I think it is "Refresh" that causes extra posting, Joe, not "Back". MSIE 4 however gives you a warning about reposting data when you use "Refresh".

In addition, quite often when posting one gets an error message that the server is too busy or the post didn't go through. The poster then hits post and post again trying to get his or her post submitted. However, it then turns out that the post did in fact go through, along with all of the re-posts. This has happened to me more than once, usually when I have composed a long post that I don't want to re-type.