However, many webmasters end up making various errors in a bid to insert the rel=canonical link in their documents as they try to specify the URL to be indexed. Explained below are common errors to steer clear of for improved indexing and ranking by major search engines.
While the <link> tag is fine with absolute and relative URLs, using relative URLs in place of absolute URLs will cause search engine bots to ignore your request. You need to specify the full path through an absolute URL including mentioning http:// as per your need, to ensure that your rel=canonical link catches the attention of all intended search engines.
Another common error is when you use the rel=canonical link to guide search engines to the first page of any article with multiple pages. You must understand that the content on different pages of an article that spans across several pages is not the same.
In such a case specifying the canonical link from page 2 or 3 to page 1 will only result in search engines indexing the second or third page before stopping further indexing. A workable option for paginated content would be to use the rel=canonical link to guide search engines to a single webpage that contains that article on a single page. Alternatively, you can make use of the rel=next and rel=prev pagination markup to solve this issue.
If you manage a website that keeps on adding new products or services in the form of new pages then adding a rel=canonical link to guide search engine bots to the latest content would cause multiple problems. This move will cause search engines to ignore the older page mentioned in the rel=canonical command while only indexing the latest page. When you need visitors to view both the older page and newer page, not inserting the rel=canonical link or only inserting a self referable rel=canonical link on the older page would be a wise move.
In case you utilize SEO plugins, you may face a problem of multiple rel=canonical links that actually lead to different URLs. You will need to thoroughly check all such links since search engines will completely ignore all mentioned canonical links in case of this error.
Again, if you copy a complete page template along with a previously inserted rel=canonical link then you may end up guiding search engines towards a wrong webpage. You need to cross-check all such links after copying templates to make sure that you have specified the correct pages on your links.
Another aspect to cross-check is to make sure that your rel=canonical link is present only in the <head> of your HTML document. Inserting this link in the <body> will result in most search engines ignoring your request. You should thus make sure that no rel=canonical links are present in the <body> of your documents and are instead only in the <head> or HTTP header.
Finally, you also need to ensure that your rel=canonical link does not lead to a URL that results in a 404 or even a soft 404. You should also make sure that most of your duplicated content is present on the canonical page while also making sure that your target page does not feature the noindex robots meta tag.
The above errors could pour cold water on your rel=canonical efforts. You should make sure that you have not committed these errors and should indulge in continuous verification of your links to make sure that your requests guide search engines to the desired pages.