Welcome to the Q&A Forum

All the methods you mention are valid as long as you nofollow them. And if having one domain to redirect simplifies your work, then go for it. Remember to always nofollow those links.

Actually, before you redirect ALL errors to the homepage, please do some reading on that tactic: http://www.rimmkaufman.com/blog/seo-and-404-pages/01022013/ http://support.google.com/webmasters/bin/answer.py?hl=en&answer=93641 http://support.google.com/webmasters/bin/answer.py?hl=en&answer=2409439 http://googlewebmastercentral.blogspot.com.au/2011/05/do-404s-hurt-my-site.html And in this: http://static.googleusercontent.com/external_content/untrusted_dlcp/www.google.com/en//webmasters/docs/search-engine-optimization-starter-guide.pdf Google specifically says (page 13) Avoid not having a 404 page at all. Finally: http://support.google.com/webmasters/bin/answer.py?hl=en&answer=83105 Use a 301 Redirect to permanently redirect all pages on your old site to your new site. This tells search engines and users that your site has permanently moved. We recommend that you move and redirect a section or directory first, and then test to make sure that your redirects are working correctly before moving all your content. Don't do a single redirect directing all traffic from your old site to your new home page. This will avoid 404 errors, but it's not a good user experience. It's more work, but a page-to-page redirect will help preserve your site's ranking in Google while providing a consistent and transparent experience for your users. If there won't be a 1:1 match between pages on your old site and your new site (recommended), try to make sure that every page on your old site is at least redirected to a new page with similar content. Google does not recommend this tactic and says "Avoid."  That's enough for me.  I don't know how to help you with the Mod Rewrite but I wouldn't 301 your 404.