1. Latest website snapshots. we can do with such sites Links that have the latest snapshot. 2. Links less suitable. the general link control 30 together within the relatively fit. 3. Site contains a large number of good articles. The more that your web site more popular, published articles the same day good ranking, this site higher quality. 4. Website Keywords ranking well. If the main keyword ranked better, then certainly high quality, so incoming links point to you is valuable. 5. Link is the html code. Some people like this get a little smart, likes to put JS in Links, or framework, it is unfriendly, we should be able to recognize it. 6. High value. link is the site of a vote, approval, and now most of the links only as a link, so we must return to the nature of links that site their high value, including alexa value, PR value, based on quality, and so on.