I currently run a pretty popular entertainment blog on the social networking/blog site Tumblr. It's only a hobby. I recently decided to purchase a domain for it & run ads on the site to turn it into some revenue profit. Anyways, the only way you can add domains to your subdomain for tumblr xxx.tumblr.com is to host it as an A Record with Tumblr's IP. For link building & SEO & everything in general, I only refer to the site as xxx.com from now on. How does this affect the SEO? What steps should I take to ensure the best possible way to increase SERPS as I'm not completely sure how an A Record works SEO-wise. And Tumblr doesn't an option for 301 redirects.