Linkrot is the tendency of hypertext links from one Web site to another site to become useless as other sites cease to exist or remove or reorganize their Web pages. A recent survey showed that almost one of every four Web pages in the survey sample contained a bad link. Observers note that the amount of linkrot that occurs can be correlated closely (and not surprisingly) with the passage of time. Links to the home page of large companies like IBM and Microsoft appear to be the least likely to "rot." However, links to pages within companies often generate "Not found" messages as a result of site page restructures or "old" material being removed. Links to pages created by students often no longer work after the student graduates.
A good practice followed by many sites is to leave the old pages in place with a message identifying the new page address or Uniform Resource Locator and specifying that an automatic refresh or redirection to the new page take place within a few seconds.
A number of Web site development and testing products provide the ability to test all the links in a Web site and report on the failing links.