OK..I have so much great content in my forum I was sad to see most of it in the supplimental index. The reason I assumed was because the page names are meaningless, the page titles are pretty much all the same and the descriptions are all the same. Even though the on page stuff is different.
So..I have had some mods done to phpbb to make titles unique and file names contain the subject line. That means though that the page file names have now changed.
This is going to leave a massive amount of 404s in google (thanks google for making me do this :)).. no way can I 301 all these pages ...there are thousands.
So...my question. How will google treat this? Will my new pages begin to show .. (bear in mind the file names and descriptions have changed b ut the content has not).. will google see the new pages as duplicates? What will happen when google finds the duplicates are actually returning a 404?
Anyway, these are the problems google forces us to create. No idea really what will happen next to be honest.
Unique titles and descriptions are in my opinion the most important step you took. Changing the "meaningless" urls is a more secondary thing -- but changing urls almost always creates a dip in rankings and traffic for a bit.
Keep us posted on how it goes. If you were already almost all supplemental, then long term this may prove to be a good step. If the old urls now return a 404 status, you should have no concerns about duplicate content.
URLs mean little in and of themselves. As long as there are less than 3 parameters in it, Google should be fine with indexing it. The page title and the meta description are far more important than the actual URL.
The biggest problem with most forum software is Duplicate Content caused by any particular "page" of content having anywhere from 3 to nearly 20 different URLs that can be used to access it. That is the real problem that needs fixing.
See my posts from 2005 and 2006 where that topic gets a lot of coverage and discussion.