Exchange of friendship links must choose the relevance of the site, first look at the status of the site, the connection is not a lot, the resources are not adhere to update, and then look at the search engine included, snapshots are not updated in a timely manner, and then the rest. If the site is not updated for a long time, it is also recommended not to exchange links, similarly, if the site is rich in content, collected in good, updated soon, can also be considered to exchange links, to learn to look at the development of a website.