Would combining sites be better for SEO?

We operate a 12-year-old group of branded Web sites that provide subject-specific technology tips and techniques. One is for mobile computers, one is for email, one is for Lotus IT professionals, etc.

Right now, they each have their own unique domain name, and are linked together by a "related sites" ribbon at the top of each page. Here's how they're ranked right now:

topic1.com: Page rank 5/10, Alexa U.S. rank 399,760
topic2.com: Page rank 5/10, Alexa U.S. rank 176,373
topic3.com: Page rank 4/10, Alexa U.S. rank 432,522
topic4.com: Page rank 4/10, Alexa U.S. rank 632,112
topic5.com: Page rank 4/10, Alexa U.S. rank 180,184

These all run in a legacy CMS and have about 100,000 pages combined. My big project is moving all of these to WordPress. In doing so, I'm also considering some SEO issues, one of the biggest being whether it's better for SEO (and, hence, traffic) to combine all five sites into one super-site, with each topic a subdirectory. So instead of topic1.com, topic2.com, etc., we'd have:

supersite.com/topic1
supersite.com/topic2
supersite.com/topic3
supersite.com/topic4
supersite.com/topic5

Obviously, this will require some quality mod_rewrite action, but the big question is this: is it better to combine them all into one site, or worse? Will I lose SEO equity by combining them, or gain SEO equity because they all have incoming links with very little cross-over between sites?

Anyway, I very much welcome opinions on this.

-- David

  • drmike

    Matt Cutts has stated a couple of times that Google now sees subdomains and subdirectories as separate sites if they're set up to be. There;s some discussion on the SEO forums if this was true or not. I can see this for subdomains but I'm torn on subdirectories. If that was true, Google would be seeing wordpress category pages as separate sites.

    My honest answer is that I would just leave it as separate sites within wp/wpmu. Any time you can stay away from mod_rewrites is better than doing them. At the very least you know you're going to screw up something along the way. (Not just you. Everybody does.) But also in addition to branding, you also have to think about customer loyalty as well as the presence of current inbound links.

    Heck, why make it harder?

  • David

    Well, the thing is that I'm going to have to write hairy custom mod_rewrite code anyway, since I'm not coming in from WordPress, but from a legacy CMS. So ALL the URLs from all those pages are going to need to be rewritten anyway. This whole project is insanely hard, because I have to build plug-ins to parse all those pre-formatted pages (all which have a form of legacy markup).

    That's why I'm looking at this question now. And I am concerned about customer loyalty. The brands are known and while I can still use the branding on the pages, that's not as strong as in the URLs.

    But each site has a limited amount of readers, and if I combine all the sites into a super-site, I have a LOT more readers overall -- and I thought that might drive up both page-rank and ad sales value.

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