Google has been trying to improve the way it detects duplicate content on a website. URLs with parameters, such as the ones used for pagination, are tricky. You have the option to add a link tag to help Google identify this content. To read more about this check out the blog post in the Google webmaster blog.

To implement this in a Joomla template you can add the code in the overrides. For example you can open root/templates/your_template/html/com_content/blog.php. Inside it add this code:

// Add rel=prev/next
// http://googlewebmastercentral.blogspot.com/2011/09/pagination-with-relnext-and-relprev.html
$doc =& JFactory::getDocument();
$pagdata = $this->pagination->getData();
if($pagdata->next->link){
 $doc->addHeadLink( $pagdata->next->link, 'next');
}
if($pagdata->previous->link){
 $doc->addHeadLink( $pagdata->previous->link, 'prev');
}

The variable $pagdata contains all the information about the pagination for the current page. We simply make a check for a next or previous page link. If there is one it means the page with other items exists so we can add the link tag. We do this with the addHeadLink function.