Nofollow is an HTML attribute, which can be applied to any hyperlink to instruct search engines not to pass on PageRank or other ranking signals to the target page. This attribute is mainly used for links that were sold for sponsorship or generated through user-contributed content, since these links cannot be considered natural endorsements of the website and may act in ways that would manipulate the search ranking system. The nofollow attribute on the link simply tells search engines to ignore the link while ranking the linked page.