If you don’t already know, duplicate content can have a hazardous effect on your SEO efforts, and we were lucky enough for Google to tell us about it in February this year. Google released an article hinting that you should specify your preferred version of your page(s). And when Google “hints” something, you’d be stupid not to make it a standard in your procedures! By using canonical links, you are telling Google which page is the “original” or “preferred” page, of a page that can have multiple variations that are identical or very similar.
What is a canonical link?
A canonical link is a <link> element specified in the <head> section of your duplicate page(s).
<link rel=”canonical” href=”http://www.example.com/products.php?prod=tyres” />
Give me an example!
If you have a page listing all the tyres you are selling, such as:
and another page listing the same information, but sorted differently, such as:
You would need to specify your preferred version of the URL on the duplicate page. Therefore, if you would like the first URL to be your preferred page, insert the canonical link pointing to that page into the duplicate page. When I mention the term “preferred page”, this indicates the page that you would want Google to list in the SERPs.
What most don’t understand.
This works perfectly well for the example mentioned above, but did you realise that even if you dont have an e-commerce site and you believe that you do not have any sort of duplicate content on your site. Chances are, you do! The URLs below are all different in the eyes of a Google bot.
And did you realise, your PageRank™ is probably being spread between some of them? This is due to the fact that others link to you differently. Its a given that you cannot control how others link back to your site, but you need to let Google know what your preferred URL is so they can transfer the properties accordingly. Inserting some code into your .htaccess file to accomplish this is a very good idea. You should also keep in mind not to have contradicting URLs in your sitemap.xml, and using Google Webmaster Tools to specify between “www” and “non www” is another must do.
Google is not the only search engine using this standard, Yahoo! and Bing have both incorporated this into their algorithms and you can read their press releases here and here. So in the hope of increasing the efficacy of your SEO knowledge, keep this listed at the top of your “SEO to do” list.