I thought this article was worth re-publishing in its entirety.
*How to Retain PageRank while Consolidating Domains*
Source: [Dr. Ralph Wilson’s WEB MARKETING TODAY Free Weekly](http://www.wilsonweb.com/art/promote/combining-domains.htm)
> “I designed a website I’ll call greatsoap.com (not the real domain), which I optimized and which ranks well for its ‘soap’ products. Now the client wants to consolidate three separate product-line websites (including the one I developed) under the company website “great.com” (not the real domain). Won’t this cause the company to lose rankings for ‘soap’?” — Mark
[Editor: For this question I called on [Bruce Clay](http://www.bruceclay.com/), founder of one of the world’s top search engine optimization companies. This is a rather technical answer, but nothing less will suffice due to respond to the nature of this important question. Bruce introduces several complex topics that you can explore further in links to his site given below.] Bruce comments:
The answer is “maybe”. In general, if you mix several separate themes into one website, you will lose the focus of the site. In essence, mixing the separate products confuses the search index to the point that you are no longer about the separate products and you are seen as less of an expert.
Let’s suppose you have the separate themes of soap, degreasers, and disinfectants. On separate sites you can be a subject matter expert on each because each individual site has a specific concentration of information. However, if you mix them together incorrectly, your site is less about each individual theme and is only about any themes that appear common to them all — according to a search engine algorithm. Even within soap, you could have laundry soap, dish soap, and bath soap themes. If you mix them together incorrectly, you could end up being about soap, but not about dish soap. In other words, consolidation causes ranking at the common denominator level if the integration is not theme- aware.
###Building a Content Silo######
Given this, you can “silo” the content. Siloing is an architectural method we invented that delineates one theme from the others within a site and essentially preserves multiple-theme focus. Each of the separate themes will still rank well, and the common theme will rank well, all at the same time and within the same site. [Editor: You can learn more about siloing content in Haylie Gibson, “Theming Through Siloing,” SEOToolSet Newsletter, May 2005 [(www.bruceclay.com/newsletter/0505/silo.html)](http://www.bruceclay.com/newsletter/0505/silo.html).]
###Protecting a Company against “Hate Sites”######
If the client even remotely can suffer from “hate sites” where “great-is-evil.com” is a possibility, and you would want to keep such unfriendly sites out of the top-ten positions, I recommend that the company retain separate sites. Consolidation will result in only one site for that “great” query, and the negative site can be in the top-three. Separate sites can push the negative site down. In fact, I would recommend the client create three more sites to protect against this event, if it is a risk.
###Dangers of Pointing Several Domains to the New Domain######
It would be a mistake to “DNS point” these domains [Editor: that is, to just point each domain name to the same IP address on a Domain Name Server (DNS).] This will result in a duplicate content filtering that will be difficult to control and may dilute the intent of the consolidation. [If done incorrectly, the same content could show up under different domains, perhaps triggering search engine penalties.] We strongly recommend that the root of the three domains be “301 Permanently Moved” to the new domain, should you choose that option. (See Susan Esparza and Aaron Landerkin, “Sorting Out Redirects,” SEOToolSet Newsletter, April 2005, ([www.bruceclay.com/newsletter/0405/redirects.html](http://www.bruceclay.com/newsletter/0405/redirects.html)). If the company you mention is a serious player, it may already own a great many parked domains, and these can be dampening rankings already. I recommend that the company implement an “IP Funnel” (we invented this as well) as described on our Server Technical Tips page ([www.bruceclay.com/seo-tech-tips/techtips.htm](http://www.bruceclay.com/seo-tech-tips/techtips.htm)).
###Proceed with Caution######
Understand that merging domains can result in subtle to severe ranking loss for targeted keywords, or (if siloed) the site can preserve major keywords and add long-tail traffic [that is, increased search engine traffic from less-used keywords]. We have seen very rapid 40% traffic increases due to siloing,and thus believe that rankings can increase if changes are carefully implemented. It is not practical to expect that nothing will change. My advice is to be very, very careful. Do not do all three sites at the same time unless there is a compelling reason. Do baselines of rankings and traffic well before and after each integration with a competent analytics tool. Expect the rankings to possibly fall as the sites are integrated, especially if they cross-link within their content. You may see no change when one site is integrated, some fall when two are integrated, and drastic fall when three are integrated due to increasing theme erosion.
Copyright 2006, Ralph F. Wilson. All rights reserved.