Canonical tag is being used to overcome the problem of duplication. You need to indicate the tag in the particular page where you have to show the original content. I am expecting the details regarding that tag
canonical tag is good but i think u can use htaccess file through set canonical code this excellent because only one time u wrotte code then easily apply all page.
Canonical is not a tag, it's a link relation. You use the following in the head area of an HTML document: <link rel="canonical" href="http://example.org/preferred-url-for-page-here"> In order to specify which is the canonical URL for an HTML document. Thus if you can access say an article via /?id=12 and /my-book, you specify one of those addresses as the canonical one, and robots then know which is a duplicate, and which address to use when referring to said page. For non HTML Document, you can use the canonical link relation inside a "Link" HTTP header.
Canonical tag is used for URL. Some time you might see any web site is using www. to open in web, but the same website is opened without using www. this is the canonical error. If your website having canonical issue, then google will index both pages i.e abc.com and www. abc . com and consider the 2nd one duplicate content. To get rid of this, a canonical tag is used so that browser auto redirect to the domain weather it is www or without www. whatever you wish to make your domain.
In this modern age where everyone and their mother has a smart phone, a lot of sites have special versions of their sites or content which is mobile friendly. The problem is is that Google and other search engines will see these two pages of content as being the same. When it finds the two pages, it becomes forced to choose one or the other to index. This is why you want to use the canonical tag so that Google can understand that you recognize that you have two versions of the same content on purpose and that they each have a purpose but Google should recognize that one version is the canonical URL.
Using canonical tags is a great way to consolidate your link juice coming from the links pointing to your page with with different paramaters into one consolidated url.
Canonical error is a big threat for a site. It is a error that a site consider two duplicate sites to each other because the open with www and without www. To remove this error put a canonical tag in header tag.
Wrong. First of all it's not a big threat to have duplicate content, or two versions of a website. Second, you don't "fix" that by using the canonical tag, you fix it using and HTTP Status Code of 301 with a redirect from equivalent pages on non-www to www (or counter, from www to non-www).