In Google there are many guidelines and policies you need to consider before developing or optimizing a website. In this article Eyewebmaster will focus about what is Shadow domains and how can you avoid being penalized by search engines especially with Google. What are the things to do with the purchased domains that is in your host especially if it is hosted by one provider?
Eyewebmaster had tried to open this up into Google forums and glad to say that some webmasters answered about the matter. First answer that was given was having multiple websites with the same content is not practically good in building up websites for your domains. It is not advisable to implement the same content to different domains just to manipulate online brand or keywords and other purposes. One reason for this is that because of their guidelines and panda algorithm update. One best thing to do here is to use a 301 redirect to a single site. This process can be done by webmasters or probably with your own html developed skills.
The second answer is referring to domains or pages with little useful content, created only to rank for few specific words or phrases, and funnel people to another site/page. They are referred to as “doorway pages”, and are against the guidelines. One of the best thing to do is to develop unique content to different website pages, create different themes for your website brand, products and other related purposes.
This summarized information could probably help you understand about shadow domain but I’ve got some video from “Matt Cutts”, the head of Google’s Webspam team, which could help us understand about the issue. This question was brought out by “Land Lubber” which is “Whats your take on add-on domain” which mostly refer to shadow domains.