what is dofollow and nofollow links in seo

rel="nofollow" is a tag that can be added to links to prevent web crawlers (spiders) from following a link and indexing that page. There is no dofollow tag, to get a spider to follow a link simply don't include nofollow.
Nofollow prevents pagerank being passed to the link from your page, plus a few other things all relating to search engines algorithms.

I agree everyone points you said for do follow and no follow links in seo. Suchlike it’s also helpful for who like to get potential traffic from online with follow search engine algorithm.

Dofollow and nofollow links are menat for web crawlers, when we mark a link nofollow then web crawler does not indexes that page and will not help you in getting benefit of link juise(PR), wherase dofollow links are messages to google so as to get link juice to your website.

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But How Check A Dofollow a Link. Any Add ons...

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Thank You For sharing good knowledge...