Why should we use Canonical tag?
We use canonical tag to avoid duplicate content
It does not consider it possible, but the major industry of Google, Yahoo and Microsoft has come together and want to do something about the unintentional duplicate content.
The idea here is that it often happens that some pages are indexed under different URLs,
The latter could be here, for example be an adapted version of the print page. The content remains (largely) the same, but now two URLs are indexed search engine. So far, so bad. So now you want to tell the search engines, which then is the “correct” URL of the page. These would be inserted in the <head> of the page the following:
<link rel=”canonical” href=”http://www.domain.com/test.html” />
And even the search engines ignore the variant with “?view=print” behind it, and everything is good.
Just sessionIDs have become in some CMS and many storefronts to a problem that is solved by this. At Thomas illustrates how you can at least get at the sessionIDs without using the new day, he used this simply. htaccess file.
For all WordPress bloggers, there is already a plugin by Yoast for Magento and Drupal. By the way, the message of the “makers” should be passed by using the canonical attribute also PageRank and link power to the “main” URL. So far this has on the existing – URLs distributed – often hundreds. The course particularly happy one.
Whether the new development was really necessary now, let everyone decide for themselves. With careful programming, you can exclude such issues from the outset. The ability to cure, by his own neglect such a tag seduced, of course, to deal with the problem just does not deal directly.