If you come accross a hyperlink with rel=”nofollow” attribute, it is a way to instruct the search engines not to follow the link. Basically links with nofollow arrtibute won’t get any credit when search engines rank websites in search results.
Ex: Hyperlink with nofollow attribute.
“www.url.com/test.html/” rel=”external nofollow”
Any link with rel=”nofollow” tag will indicate to search crawler that the page shouldn’t be followed, which internally won’t contribute weight for page ranking. nofollow isn’t a negative vote, it is way to make sure that spammers won’t get any benefit. This will improve the quality of search engine results. Attribute value nofollow specification was designed by Google.
Blogging platforms like WordPress by default add the attribute rel=”nofollow” to the hyperlinks in comments and trackbacks sections.