Websites that are able to amass a large number of links from related websites that contain relevant content, tend to have an advantage when attempting to rank well in the large search engines. The tricky part is understanding how to build a large quantity of quality links. With the growth of the web and increased competition, search engines are weighing link relevance, and link authority as part of their ranking algorithm

Earning Links
Link popularity is a form of "social bookmarking". Think about it, a link is akin to a "vote" from the source. Just like in the real world, a vote from a source that is known to be trusted and respected in a specific industry carries more weight and contains more social clout, so does a link from a credible online source. Web links are seen as a recommendation or a website endorsement. If the endorsements are from established respected sources in a specific sector, the link is weighed heavier than an unrelated link or links from a source that is not yet established.

The easiest way to earn a link is to provide quality unique content.

How do you know who is respected?
One way to determine the value of a website is by accessing its PageRank. PageRank is visible in the Google Toolbar and is calculated based on the number of quality incoming links that a website has. Alexa Rank and TrustRank are also indicators of a websites popularity. Alexa tracks the websites that people who use the Alexa toolbar visit. Based on these visits, they determine the popularity of a website and rank it accordingly. TrustRank is a little more difficult to pin down. TrustRank is based on the assumption that good websites rarely link to bad neighborhoods.

PageRank and Alexa Rank can be used to help webmasters assess what webpages and websites are valued by search engines. Keep in mind, this is not an end-all/be-all. The rankings should only be used only as guides. Relevance matters, a link from a respected tree website will not help a software website unless they are selling software related to trees or landscaping.

Authoritative Links
Some websites wield great power. They are not topic specific and are considered quality credible sources or "authorities". Examples of authoritative sources would be other search engines or directories like Yahoo, DMoz and Wikipedia. They are respected resources on almost any industry topics. Authoritative links are desirable and can help increase a websites popularity.

Deep Linking
Regardless of a websites topic material, if the website is well designed and informative, its generally not too difficult to attract links to a websites' main page. But what many webmasters do not realize, it is equally important to attract incoming links to a variety of pages on the website. The more varied the links to various webpages within a single domain, shows search engines that a website contains an abundance of quality material.

Anchor Text
When a publisher links to a website, the search engines consider the link text used in the link. Varied but related text in the link shows what the material is about. All links that contain the same text look "unnatural" and may be considered as "purchased" or unreliable. Search engines are partial to natural incoming links. Ideally attempt to establish varied linking text that unite in a common theme.

An example: Software Marketing Resource http://www.softwaremarketingresource.com has a number of links with text containing things like: software marketing; shareware marketing; software promotion; online software marketing; promoting software; promoting shareware. All are synonymous with software marketing and are natural phrases that would be used to describe the same website.

Directory Linking
Directories should not be overlooked in linking strategies and while webmasters should not rely on directories solely when developing strong links, they can be advantageous. Particular attention should be paid to topic specific directories. A topical directories are often consider authorities and a related link can boost exposure.

Competitive Intelligence
Webmasters looking for links and don't know where to look, should have a peak at who is linking to their competitors. Use competitive intelligence to track down quality link sources.

Give it Away
An easy way to earn links is to give something away. Whether you are providing quality content free of charge or a free software application, webmasters appreciate quality content and products that are available free of charge. Use the free item or content to draw attention to your website, if you are truly providing something of value, it will generate unsolicited links that are invaluable. Develop a linking strategy as part of your website marketing plan.

The aim should be to attract authoritative links from related sources.