Today, I learnt about cononical linking. Canonical linking is a way of letting search engines know that your content is accessible through multiple URLs, by publicly specifying the preferred URL of page content. This prevents Google penalising your site for having duplicate content.
I first came across the possibility of search engines penalising sites for duplicate content when following WPDesigner’s excellent tutorial on creating WordPress Themes. Here, he recommends ways to change the content of pages which might be viewed as duplication by Google – Prevention not cure.
It wasn’t until today that Mike recommended that I “canonically link” Rose Theatre event pages because they are almost identical to the same page in the events section of the site. To do so, within the <head> tags of each Rose Theatre event page, add a link like the one below:
<link rel="canonical" href="http://www.edgehill.ac.uk/events/2010/03/09/stand-up-comedy" />
The link tag is an empty tag, and the use of the “rel” attribute defines the canonical nature of the tag. In our case we generate the link URL using symfony routing rules, URL parameters and the page slug so we don’t need to add the link for every page.