301 Redirects 
One thing I ran across while looking for the best way to minimize search engine dips when doing site redesigns is the notion of a 301 redirect. I had never heard of a 301 before but the more deeply I dug into my research, the more it became clear that I was going to have to have at least a preliminary idea of what a 301 is.
Basically, a 301 redirect is some code you can put in your .htaccess file for servers running Apache. It tells spiders that a page has moved permanently, giving both the old and new URLs. 301s can be used for entire sites or for specific files within a site.
People seem to agree that a 301 is the best way to go when changing domain names or relocating or renaming certain pages on your site. With domain name changes, an older domain name will generally fare better than a newer one, but even so, having a 301 in place will help minimize the impact of the change.
One solution to this that might be the best of both worlds might be to go ahead and build the new site, 301 the new pages to the old, wait a year, then 301 the old pages to the new. For example, for my page
http://www.bend-in-the-river.com/qapersonality.html
I could build basically the same page in my new site (with the domain name alias reversed as discussed in previous posts), and, to help with findability, change the URL to
http://www.susanlitton.com/personality-disorders-questions.html.
I could then put a 301 on the susanlitton page to redirect it to the bend-in-the-river page. After a year, I could switch it: 301 the bend-in-the-river page to the susanlitton page.
Writing 301s doesn’t appear to be difficult. For specifics on how to write the code, I found this article helpful:

RSS
[…] The best ways to redirect traffic are either 301 redirects, which I discussed in an earlier post, or mod_rewrite. I tried to find a solid source that could tell me why you would use one of these over the other. I don’t feel I’ve found “the” answer yet, but it seems like if you’re making a lot of page and folder name changes, that mod_rewrite might be easier. However, mod_rewrite is only for servers running Apache, whereas I think 301s can be used with other server software. […]
Pingback by Findability Blog » mod_rewrite — February 24, 2007 @ 10:25 am
I’ve also learned that there are ways to do 301s on Windows servers. If you’re interested, Google 301 redirect Windows and you should find plenty of info on how to do it.
Comment by susan — February 24, 2007 @ 10:59 am