It’s almost not worth mentioning, but I know one website noticed this, so I’ll talk about it. Last week there was an update to how we canonicalize a small number of urls. What is “canonicalization” again? Read this previous post, or see this post by John Andrews to see all the ways that you can have the same content on urls that are technically different. Some people ask “Why don’t you just assume www.example.com and example.com are the same?” The answer is that they don’t have to be, and for some websites they are different. For example, http://phpicalendar.net/ is a different page than http://www.phpicalendar.net/. This happens more often than you might think; FindWhat has different www vs. non-www pages, for example.
Okay, back on topic. The data for externally visible PageRank didn’t change. The only way someone would notice their PageRank changing last week is for example if they were checking for a different canonical url (e.g. externally visible PageRank is shown for www.example.com, but Google changes the canonicalization from www.example.com to example.com).
That’s a really rare situation, as evidenced by the fact that not many (any?) people in the blogosphere noticed any PageRanks changing. In general my advice is not to worry that much about changes in canonicalization (if you can see your PageRank on either one of www.example.com or example.com, Google generally has your PageRank stored and uses it correctly in scoring).
For the people who want to make sure that all their webmaster ducks are in a row on this topic, here’s my two-minute advice:
– Pick one way of writing all your urls and use that consistently in your pages and your links.
– If you pick (say) www.example.com as your preferred root page, make sure that you have a permanent (301) redirect from pages such as example.com to www.example.com. Michael Nguyen has a nice short post about how to do this in Apache, or Beyond Ink shows how to do a 301 redirect on several platforms.
– To be extra safe, feel free to use Google’s webmaster console to specify the preferred root page of your domain (www.example.com vs. example.com). Read this post by Vanessa for more details.
Whatever you decide, I recommend that you make sure that your choice is consistent. These short steps will help search engines refer to your site the way that you want people to refer to it.