Check this example... A web page may be accessible using many different URLs such as:

www.example.com
example.com
www.example.com/index.html
example.com/home.asp

Each of the above URLs are typically seen by the search engines as if they are different pages on your site and are represented as such in their database or index. From a search engine perspective, this can cause a bit of an issue. Hence the idea of canonicalization. Canonicalization is the process of picking the best URL (to present to the search engines) when there are multiple choices available. Typically a search engine, such as Google will attempt to pick the best URL that they feel is the authority for that page.

Every page on your web site should be referred to using one and ONLY one URL. This single URL for a page is called the canonical (preferred) URL.

How Canonical URL’s Affect Your Web Pages

When there are more than one urls pointing to the same content each url is treated as an independent web page by the search engines and hence when the content is compared with each other it appears as mirrored site to the search engines.

Mirror sites are those which are set up just to scrape off content from other sites and paste it in their own site.

Search engines are very serious about copied content and if you dont solve the canonical url issue your entire site will mirror itself and that is what I meant by “your own blog will eat your own blog”.
How to solve the problem of Canonical URL’s?

There are ways to solve URL canonicalization using server side scripting or from your cpanel from your hosting account.

The simplest methods are...

Enabling Permanent Redirect From cpanel to Specify Preferred Canonical URL

Using the rel =canonical attribute

Htaccess file To Define Canonical URL [301 redirect]

Canonical URL is the search engine friendly URL that you want the search engines to treat as authoritative. Lack of a canonical URL will cause duplicate content issues since each URL renders the exact same content. Each URL in the search engine’s index will have the same content associated with it.

The lack of URL canonicalization also leads to split link juice and split page rank issues. Because there is no single canonical URL for the page in the above example, the non-canonical URLs are essentially taking credit for inbound links to your page that should instead be focused on a single canonical URL.

SEOfit.Com - Learn SEO Basics & Terms - SEO Topics of this page
About canonical or preferred URL URL Canonicalization Process search engine friendly canonical URL How to Define Canonical URL canonical attribute information Canonical URL & duplicate content About canonical url - canonical tag canonical url & page rank issues Canonical URL redirect methods