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Putting aside the ethical issues of having two clients in direct competition, Google cares far less about the template you use and more about the content and service that you provide. Both will be indexed. Don't duplicate anything that isn't technical in nature. There are hundreds of blogs that share the same templates, hosting platforms, etc. If one gets deindexed, talk to Google directly.

If you're serving multiple target audiences, then this is entirely white hat. If you're doing it for usability (segmenting products based on category), it's white hat. If you're doing it to own the top 8 listings instead of the top 4 for the same search terms, that feels grey hat.

Yes. 301 simply means "Hey Search Engine, this page has moved to here." It'll pick up the change.

My theory is that there are now two ways of using the Web. Modern, experienced Web users don't really rely on the "fold" to read a site. Their first action is to skim. There's still a class of Web users who treat the Web like a television. They click onto a site and "view" it. How does your audience use your website?

Q1: Both of those pieces of code mean the same thing. You can use the "attributes" (href, rel) interchangeably.

Q2: It stops page scrapers.

**There's a lengthy discussion on it here: **https://developers.google.com/webmasters/mobile-sites/mobile-seo/configurations/separate-urls?hl=en

Notably this section:

For Googlebot, we do not have any preference and recommend that webmasters consider their users when deciding on their redirection policy. The most important thing is to serve correct and consistent redirects, i.e. redirect to the equivalent content on the desktop or mobile site. If your configuration is wrong, some users may not be able to see your content at all.

In my opinion, trying to figure out what Google does on the backend is a losing proposition. Maybe they index both; maybe they index one. Heck, there's no way to know if they even index full text now for every site. There's certainly a lot of optimization going on in the back-end that is above and beyond our purview as SEO practitioners.

Google says they don't care what kind of redirect you use for mobile. Likely, that means your mobile sites are being semantically linked to your desktop version of the pages -- they specifically recommend against pointing two separate page redirects to the same mobile page. They recommend that you add a link that lets mobile users click over to desktop for usability. That's good enough for me.

Rewrites are generally regarded as the best way to handle this kind of redirect, but your DNS provider likely has their own redirect system in place that can implement the same functionality without modifying your site's .htaccess. Same result, different technique.

The reason I use my DNS with a "www" subdomain record to forward to my non-www domain is because WordPress sometimes has issues with using RewriteRule. It seems to break permalinks. I always just set it once with my DNS host and never think about it again.