We hope you use the rel=canonical tag to tell search engines what version of duplicate pages (eg. http://yoursite.com, www.yoursite.com) you prefer to be indexed. This tag is supported by all major search engines: Google, Bing and Yahoo. However it’s sometimes rather tricky to configure this in a proper way. In this article we put together some good questions about rel=canonical, that have been asked by Web CEO users.
Should I use rel=canonical, if I have several product pages that differ only by a sentence or two (different colors and sizes)?
Yes, we think it’s appropriate to use a rel=canonical tag on very-near duplicate pages. For example, do this if you have several URLs with very similar products on them. However, you shouldn’t abuse this tag, because search engines may just ignore your tags.