We have had two new clients come to us for Internet Marketing recently AFTER redoing their websites. In both cases whoever made the changes had no clue of or ignored this basic fact:
Changing website page names or your whole URL is the exact equivalent of a physical move. If you don't put in a change of address, how is anyone going to find you?
The answer of course is... they can't. At least not easily or quickly.
Any links from other websites to changed pages will no longer work.
Google will think you're gone.
Bookmarks will be invalid.
This is particularly dumb because Google has made it both easy and easily known how to deal with this situation (their recommendations mostly work with other search engines as well). And it is far more easily dealt with before being messed up than afterwards.
It can take months to recover rankings and traffic after an improperly handled move or restructuring of a website.
The following is just a list of the key points, I'm not going to try and explain the technicals in this post:
Now each of these is rather easy to do. If done right, any disruption to your rankings or traffic are minimal if any.