Specify your canonical : Google lets you specify the “one true URL” for content, if that content can be accessed from multiple URLs. You add a LINK tag like this:
Google will take that into account in its index, apparently.
Joomla really needs this. That CMS seems insistent on allowing you to have content under more than one URL.
[…] we now support a format that allows you to publicly specify your preferred version of a URL. If your site has identical or vastly similar content that’s accessible through multiple URLs, this format provides you with more control over the URL returned in search results. It also helps to make sure that properties such as link popularity are consolidated to your preferred version.