A Canonical URL, is a URL specifically intended to hold content. Sometimes servers may be configured incorrectly, which could make the same content accessible on different URLs.
A common situation where this may occur, is when using the WWW subdomain. Another is when the directory index file (I.e. index.html), is accessible both from http://brugbart.com/index.html and http://brugbart.com/
There might also be other reasons why you want to use the Canonical tag – maybe you have two different versions of the same page. I.e. One for web, and another for printing.
Canonical URL Tag
Sometimes you might not be able to configure the server properly, for whatever reason – usually due to host specific limits. In those cases, you may want to include a Canonical URL Tag, which tells the search engines which URL you want to show up in the SERPs.
Including the below code in your head section, would suggest that only http://brugbart.com/ be used – just replace Brugbart with your own domain name.
<link rel=”canonical” href=”http://brugbart.com/">