Add Nofollow Tag To All External Links

In Blogger, importance of Nofollow and implementation of Nofollow attributes on external links, categories, tags, labels and comments in blogger. At first it is necessary to learn what is no-follow attribute. It is clear from the name Nofollow that it stops to follow anything.
In the field of SEO,  this attribute is used in a hyperlink that tell search engine crawlers to not to follow and crawl the specific link. Rel=”nofollow” is used to control the flow of PageRank from one website to another. In other words rel=”nofollow” attribute is used to maintain the page rank of your website. And it orders search engine crawler to stop the crawling of the destination link. To serve the purpose, I will use post editor and template modification to add Nofolow tag to all external links and comments in Blogger.

How to Make All External Links Nofollow automatically

Login to your Blogger Dashboard >> Template.
Click on the Edit HTML button.
Find the </head> tag by pressing ctrl+f  and typing </head> in the search box.
Now add the following code above the </head> tag :

<script src='http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.js' type='text/javascript'></script>
<script type="text/javascript">
    jQuery(document).ready(function () {
        jQuery('a[href*="http://"]:not([href*="http://www.yourdomain.com"])').attr('rel', 'nofollow');
        jQuery('a[href*="https://"]:not([href*="https://www.yourdomain.com"])').attr("target", "_blank");
    });
</script>

Do not add Jquery if you have JQuery plugin installed.