When re-designing a website, there are a great many considerations that need to be made. On the whole, good webmasters catch the most critical elements, but one area that seems to get consistently overlooked is inbound links. Often times when the site is restructured, the fate of all of these links can get overlooked. Inbound links must be treated with the utmost respect since they direct visitors to your website and affect your PageRank as well. Links from search engines to your site need special care. If your server is returning a 404 for a link, the SE will eventually drop the link from its list and the replacement content may not get spidered for a long time.
The Problem
When a search engine spiders your site and receives a 404 status code for a link, the search engine makes a note that the link was not found, and after a few such experiences removes the link from their list of links to crawl on your site. By properly redirecting a search engine to content that has been relocated, you retain these valuable links that have been built over time.
Web server attempts to serve page: /OldAddress.htm
"Page Not Found" condition or 404 is encountered by web server
At this point the web server's first instinct is to serve the default 404 page. This in many cases is the default text "Page Not Found" generated by the web server when a requested file cannot be located. This is where we want to step in and try to salvage the visit for the customer.
We addressed this issue with a client that had hundreds of search engine links and inbound links from other websites. This client was unique because their inbound links were not from link exchange programs but from actual customers who found their product interesting. This meant that each link was critical to our client as the quality of each inbound link was very high. The new structure of the website dictated that ALL pages would have new addresses and none of the old addresses would fit into this scheme. The structure of the old site did not allow for any single elegant mod_rewrite regex hack, so we needed something a little more extensive.
Search Optimization 
