Originally Posted by J.P.

I programmed something that might be called AJAX around 2000 for a portal-like site of mine. Users could change the color of headings, rearrange the windows (drag & drop) and stuff like this and it all got saved in the database using HTTP requests to a hidden image. It really was not AJAX, because it did not use XML back then but it did it's job pretty nicely

I also programmed a message board around the same year that showed a tree of replies and when you clicked on a user, a request to a hidden frame occured which then changed a content of some DIV to show this user's message. Also not really AJAX, cause it did not use XML But you could read the whole thread without refreshing the document and that's the whole AJAX idea, isn't it?