Posted: 10 Apr 2013 12:29 PM PDT
content duplication, you'll often hear about the term 'rel=canonical'. This is often used as a SEO technique to avoid penalty, because search engines will penalize you if you have duplicate content on multiple pages. This happens when you deliver archive pages, data sorted according to the user's preference, and so on. Rel=canonical is used to overcome such problems, and helps consolidate all different versions of the same page. It tells search engines what URL to consider and display in search results. Useful as it is, rel=canonical can be a bit tricky to implement properly.