Google's

When referring to the "Nofollow" Tag we mean a tag used in html language and has become fundamental in the functioning of the search engines. Its insertion allows you to exclude certain links from scans by the engines, which are useful depending on the conditions dictated by the search sites. Different sites apply different policies on the subject. As for Google, the choice is to pay particular attention to paid links as these would affect search results.

Another condition, requested by the Mountain View search engine, is that of the application of the Nofollow tag for links from untrusted content: even in this case the link in question would not affect the page rank and, above all, the aforementioned links not appearing in search results would be less subject to spammers. Lastly, Google asks webmasters to apply the tag in such a way as to exclude from search list pages of little interest, which can be those of the Login. This system reveals this tools utility also in regard to the site itself, which is placed in a position to highlight certain links in the user's eyes which makes use of the search engine, excluding others considered secondary. It should be underlined that this is how Google uses the Nofollow tag, and how other search engines apply the Tags function differently.

For example, Yahoo! foresees the archiving of the page marked by the Tag, which is not foreseen by the Google engine's indexing. Another example that highlights the different policies adopted by the other search engines is the propensity to show the existence of links marked by the Nofollow: while Google shows its existence only in case of previous archiving of the page, both Yahoo! and Bing do not show the existence of the link in any case.