I was doing some web design work for a friend/customer of mine, and he had a Web Hosting account with a company that used cPanel. I’ve used cPanel before, I’ve dabbled in it and fixed problems with it. But never really used it extensively as a client so to speak. Anyways, included in the customers Web Hosting package was 20 Addon Domains. What are “Addon Domains”?
http://cpanelguide.net/addon.php
Basically it allows you to run mutiple websites off your single account/domain name. Brilliant idea, if it was done properly. When you add an Addon Domain, it creates a folder in your main sites public_html folder, typically its name is that of your domain name. Lets just say that my customer has two domain names, the main one bob.com and an additional one jill.com
The customer creates jill.com as an Addon Domain, all is swell. Until they find out they can access the addon domain at “jill.com” and “bob.com/jill.com”. Why is this bad? Well google will see it as duplicate conent and your site will either never get indexed or have funky SEO results.
How do you fix it? Change the root directory to not be placed inside the public_html folder and viola, no duplicate content. Also make sure to edit the subdomain to forward to the correct URL as well or more duplicate content will exist.