Reciprocal links

In the field of search engine optimization, link building describes actions aimed at increasing the number and quality of inbound links to a webpage with the goal of increasing the search engine rankings of that page or website.

Link building can increase the number of high-quality links pointing to a website, in turn increasing the likelihood of the website ranking highly in search engine results. Link building is also a proven marketing tactic for increasing brand awareness.

Editorial links are the links not acquired from paying money, asking, trading or exchanging. These links are attracted because of the good content and marketing strategies of a website. These are the links that the website owner does not need to ask for as they are naturally given by other website owners.

Resource links are a category of links, which can be either one-way or two-way, usually referenced as "Resources" or "Information" in navbars, but sometimes, especially in the early, less compartmentalized years of the Web, simply called "links". Basically, they are hyperlinks to a website or a specific webpage containing content believed to be beneficial, useful and relevant to visitors of the site establishing the link.

In recent years, resource links have grown in importance because most major search engines have made it plain that—in Google's words— "quantity, quality, and relevance of links count towards your rating".

Search engines measure a website’s value and relevance by analyzing the links to the site from other websites. The resulting “link popularity” is a measure of the number and quality of links to a website. It is an integral part of a website’s ranking in search engines. Search engines examine each of the links to a particular website to determine its value. Although every link to a website is a vote in its favor, not all votes are counted equally. A website with similar subject matter to the website receiving the inbound link carries more weight than an unrelated site, and a well-regarded site (such as a University) has higher link quality than an unknown or disreputable website.

The text of links helps search engines categorize a website. The engines' insistence on resource links being relevant and beneficial developed because many artificial link building methods were employed solely to "spam" search engines, i.e. to "fool" the engines' algorithms into awarding the sites employing these unethical devices undeservedly high page ranks and/or return positions.

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Wikipedia