In this illustration from the “PageRank Citation Ranking” paper, the authors demonstrate how webpages pass value onto other pages. The two pages on the left have a value of 100 and 9, respectively. The page with a value of 100 has two links that point to the pages on the right. That page’s value of 100 is divided between the two links, so that each conveys a value of 50. The other page on the left has three outgoing links, each carrying one-third of the page’s value of 9. One link goes to the top page on the right, which ends up with a total value of 53. The bottom right page has no other backlinks, so its total value is 50.
There is another way to gain quality backlinks to your site, in addition to related site themes: anchor text. When a link incorporates a keyword into the text of the hyperlink, we call this quality anchor text. A link's anchor text may be one of the under-estimated resources a webmaster has. Instead of using words like "click here" which probably won't relate in any way to your website, using the words "Please visit our tips page for how to nurse an orphaned kitten" is a far better way to utilize a hyperlink. A good tool for helping you find your backlinks and what text is being used to link to your site is the Backlink Anchor Text Analysis Tool. If you find that your site is being linked to from another website, but the anchor text is not being utilized properly, you should request that the website change the anchor text to something incorporating relevant keywords. This will also help boost your quality backlinks score.

So, as you build a link, ask yourself, "am I doing this for the sake of my customer or as a normal marketing function?" If not, and you're buying a link, spamming blog comments, posting low-quality articles and whatnot, you risk Google penalizing you for your behavior. This could be as subtle as a drop in search ranking, or as harsh as a manual action, getting you removed from the search results altogether!
We help clients increase their organic search traffic by using the latest best practices and most ethical and fully-integrated search engine optimization (SEO) techniques. Since 1999, we've partnered with many brands and executed campaigns for over 1,000 websites, helping them dominate in even highly competitive industries, via capturing placements that maximize impressions and traffic.
The majority of web traffic is driven by the major commercial search engines, Google, Bing, and Yahoo!. Although social media and other types of traffic can generate visits to your website, search engines are the primary method of navigation for most Internet users. This is true whether your site provides content, services, products, information, or just about anything else.