Outbound links to other websites are often placed on a website, for example to refer to other information on a topic. However, sometimes website operators would like to avoid a search engine following the outgoing links. This is common, for example, for Wikis and forums in order to avoid spam or manipulations to benefit link building. The link attribute or microformat "nofollow" is one way to set a sign for search engines that the link should not be followed. This can be applied to entire websites or to individual links.