Notifying Google of a Major Site Overhaul

In a few weeks, my organization will be removing our old Web site from our Web server and replacing it with a completely new site. The new site includes completely new content and a radically different structure.

We will be using a Google Custom Search Engine as our internal search engine on the Web site.

I am curious if anybody has any advice on how we should handle this situation.

Obviously, if at all possible, I would like to remove all of our old URLs from Google’s index and have it completely re-index our site from scratch. Otherwise, visitors using our internal search engine will most likely get a huge number of search results that return 404 pages. Where there may be only one or two pages on our new site that match the entered search criteria, it’s possible that our visitors will get anywhere between 10 and 50 results from the old Web site when searching that criteria. If at all possible, I would like to avoid this.

However, I do not want to damage our search engine ranking in any way, so I am a little nervous about doing anything too drastic when making the switch.

As of today, I have Google indexing our new site at a temporary sub-domain, which I will redirect to our real domain once we make the switch.

Obviously, I will also set up the server so that any URLs to non-existent pages generate proper 404 messages, hoping that Google will automatically remove those pages from its index.

Our new Web site has a dynamically-generated Google Sitemap (whereas our old site doesn’t even have a Google Sitemap – mostly because even I have no idea what pages are on the site or where they should be). I have also put a lot of effort into utilizing keywords and page descriptions, adding RSS feeds where applicable and implementing methods to make sure content gets updated regularly. As an organization, we have also made an effort to write much more user-friendly (and search engine-friendly) content for the site.

Has anyone else gone through this? How did you handle it? Do you have any specific advice for me? Thank you.