Firstly I apologise for my duplicate posts, having discovered it happens, I should have taken more care with the back button. This is unlikely to be of value as it is 3rd party software and as my own memory is a little foggy (it's a few years ago...) but I do remember encountering what at least seems at top surface to be similar when I wrote my own forum software. In that case and as far as I can remember... I had the code to view and to post in one php script. Let's call it topic.php. What seemed to happen was the post to topic.php got caught up in the browser history and using a browser back button would refresh the page complete with the "post data". The solution, I think, was to have topic.php post to say post.php and then have post.php preform an HTTP redirect. That way, the page that did the posting did not get caught up in browser history. Doubtless this system is more complicated but I still think that they behaviour where a back button triggers a repost is something that that the forum code should and ought to be able to prevent.