What is a mirrored website? A mirrored website is one that looks pretty much the exact same as another one of your websites. For example, if you have website #1 which is www.abc.com, and then create website #2 www.123.com which is almost identical as your first website minus a different domain name. Google refers to this as being a mirrored website.
Unfortunately, there are many issues and repercussions that you have to look at when deciding on whether or not to have a mirrored website. I would highly recommend NOT doing this as Google has stated many times that it does not encourage this practice. I have also witnessed many websites being banned because they are mirrored websites. If the big G (aka Google) sees this as a way of gaming the system, you could see yourself in trouble.
I speak to many customers who want to replicate a website they own for a different market. For example, Mary sells shoes online in Canada, but now wants to sell her shoes online in Australia too. The dilemma facing Mary is that her .ca Canadian website has almost zero chances of ranking in the Australian search engines. I know this because I have used Google Australia many times and haven’t seen a single instance of Canadian websites ranking in it. What does Mary do? She creates an identical website to her Canadian one and puts it on a .com.au website. This makes perfect sense on paper, but Mary unknowingly has created a mirrored website which isn’t exactly ethical.
Take the time to make the new website as different as possible. This involves different photos of your products, different product descriptions, etc… The design can stay the same, but the content cannot. This not only will help you create a better product for your new audience, but you no longer run the risk of being banned by Google for duplicate content.
If you want to see a great example of this checkout mtv.com, mtv.ca, and mtv.com.au . The website layout and design is almost identical, but the content is presented differently with a unique flavour for each country that they have mirrored the website in.
I hope this answers a few questions that I have been receiving, please if you have any more questions you want answered please e-mail me at firstname.lastname@example.org