This question is answered by Matt Cutts in this video. If you move or update a website it’s important to redirect old pages to the new ones. Without a redirect you will loose your rankings in Google and maybe you will loose your visitor too, because he has followed a link from some other website. If you need to redirect your old pages to the new ones, it’s important to match them as good as possible. Don’t redirect all old pages to your new homepage!
Does a 301 redirect lose any PR or link juice?
Last updated: 2016-04-11