Don’t rely on Google

A while back, Google introduced the Canonical Link Element to help site owners deal with duplicate pages getting indexed in Google (such as printer friendly pages, which have almost exactly the same content as the original article).

It’s very widely used now but it’s not 100% accurate and if you make a mistake with it (which can happen) then don’t expect Google to help you out, as this experiment shows.

For what it’s worth, I don’t use it on any of my sites.  You can build a site without having to bodge duplicate content up.