The recent explosion of information available upon the world wide web has made the medium a useful source of information of all kinds.
Some web sites require authentication before information can be accessed.
Authentication can be annoying at times. Many of the sites that require authentication do so even though no sane user would care if anyone else used his account. Ideally, users would be able to use the same user ID at each site. In practice, this is not always possible. Using the same password at each site can be a security risk, since you don't know who has access to this information.