301 Redirect a Parked Domain to Avoid Duplicate Content
A lot of companies who have a website often purchase variations on their domain name to catch visitors who may type in .co.uk instead of .com or may misspell or use a common abbreviation of the company name, whilst also preventing competitors from registering these domain names. Usually, rather than showing visitors a blank (or error) page, the company will park the domain name on their main domain to help point visitors to the company website.
A common mistake is to not 301 redirecting the parked domain name to the main domain name. The problem that arises is that the search engines now see two (or more depending on how many domain names are parked) websites with exactly the same content and will penalise individual pages from each domain which they see as the duplicate page. This will also detract weight from the rankings of the website as a whole. So by adding a 301 redirect from the parked domain to the main website you will not only prevent the previous explained scenario, you will also be telling the search engines that previous pages they have indexed from the parked domain have not disappeared but have moved to the equivalent page on the main website. This should prevent you from losing any rankings that may have been gained through the parked domains.
A common way to 301 redirect is to use a .htaccess file with the following code:
RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_HOST} ^www.parkeddomain.com [NC]
RewriteRule ^(.*)$ http://www.maindomain.com/$1 [R=301,L]
This will redirect any of the parked domain name webpages to the main domain name equivalent, for example: http://www.parkeddomain.com/about-us.html would be redirected to http://www.maindomain.com/about-us.html and so on.
