how to use canonical tag?
 

what is canonical tag and how can i use canonical tag for different tags pointing at same post?

The URL from item a) is often the result of a CMS system with a search engine unfriendly URL. The URL from item b) is friendly for the search engines, it is readable and spiderble. However, there is just 1 problem: you have double content. Two different URL's but with the same content. One links to a and the other links to b. This is where you leak pagerank.

How do you add tha tag?
The rel=canonical can be added in the source of your webpage :



The url of a canonical link can be a relative link. However, we advise you to use absolute links to prevent problems. The canonical link can only link to a page with the same domainname.

Canonical Tag is used to deal with Duplicate Content. The canonical tag is a tag used to tell search engines which version of a page is the desired or preferred version.