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If you want to keep any SEO value from inbound links that go to any of those older pages, you'll want to 301 redirect them to a similar page (i.e. a top category page). According to Rand Fishkin's Moz blog writeup, Are 404 Pages Always Bad for SEO? http://moz.com/blog/are-404-pages-always-bad-for-seo "When faced with 404s, my thinking is that unless the page: A) Receives important links to it from external sources (Google Webmaster Tools is great for this) B) Is receiving a substantive quantity of visitor traffic and/or C) Has an obvious URL that visitors/links intended to reach It's OK to let it 404." According to Moz's Redirection SEO Best Practice: http://moz.com/learn/seo/redirection ... you want to use a 301 redirect to indicate that the content has moved permanently. Here's a post that describes how to create a more SEO friendly migration, here's a great info graphic: http://moz.com/blog/achieving-an-seo-friendly-domain-migration-the-infographic Hope this helps! Thanks, -- Jeff