> It sounds like what you want to do is what the history 
> section of any page on wikipedia.org site does.

I would have thought it more likely that a site like Wikipedia would
maintain the diffs, and generate old versions of pages by applying the
diffs. But I've no idea whether that's what they actually do.

In any case, I doubt they work from the HTML: they have their own document
model and their own markup language.

Michael Kay
http://www.saxonica.com/