mira:
http://www.tamingthebeast.net/articles3/spiders-301-redirect.htm
Cita: The right way - a htaccess 301 Redirect
A 301 redirect is the most efficient and spider/visitor friendly strategy around for web sites that are hosted on servers running Apache (check with your hosting service if you aren't sure).
It's not that hard to implement and it should preserve your search engine rankings for that particular page. If you *have* to change file names or move pages around, it's the safest option.
A 301 redirect is implemented in your .htaccess file.
ejemplo:
redirect 301 /old/old.htm http://www.you.com/new.htm
mas paginas:
http://www.desarrolloweb.com/articulos/cambio-url-redireccion-301-htaccess.html
http://google.dirson.com/posicionamiento.net/redireccion-301/
http://techtastico.com/post/%C2%BFque-es-la-redireccion-301-y-como-hacerla/