Active links
Periodic review is required to verify that all links are still active. Automatic review of links should help to quickly identify targets that are not valid anymore, but human review of links may be needed to ensure validity of content. Use of persistent URIs may help to avoid some of the problems created by these references. Links that go to pages with critical information should provide indication of the last verification date as an Mfield (, <… class=”linkverified”>).
Dead links
Care should be taken that all Web links are up-to-date. Dead, inactive, or missing links severely detract from the quality of a Web site. Webmasters should periodically verify that all links are still active. Many times, links become out-of-date, and merely serve as placeholders for the actual Web link. Web sites demand periodic maintenance to insure that links are current. Automated tools exist that check the existence, if not veracity, of Web links. Web masters may want to refrain from overspecifying Web sites in order to avoid Web link obsolescence. In general, the greater the specificity, the more likely the link will become outdated. On the other hand, a more generalized Web site address can force the user to burrow down several layers in order to get to the precise Web site needed. The Web master must find a happy medium between overspecifying the Web site link and forcing the user to do extensive searching once connected to the link in question
Absolute and relative links
Links within a Web site should be relative to the linking page, and not to the site root. Sites may wish to establish a reference point for relative references (e.g. top-level directory) and use to establish the reference point (use of the BASE tag may complicate site relocation). Links to external Web sites should use persistent URIs, where available. Site pages intended for external reference should provide persistent URIs, where applicable. Digital Object Identifiers (DOI), as defined by the DOI Foundation32, may be useful as persistent URIs. See 4.2.8 on site/page relocation.
Links to protected Web sites
Links to protected Web sites should, in general, indicate that the Web site is password protected or requires a subscription or registration. This annotation can be color-coded for maximum effect, in order to alert the user to the restrictive nature of the Web site.
Offsite warning
Clear indications may be needed when leaving a site for other sites, this may be related to a change of security domains, or to assure that the seamless nature of the Web does not mislead the user about the source of the content. Links that lead offsite may be tagged with “” as a method for creating a CSS controlled visual distinction. Depending on the situation, it may be useful to require browser’s to use this information to implement specific policies such as managing the history information (or cookies), blocking transfer, presenting the link with some warning icon, presenting the user with some “leaving xxx site” warning, etc. As an alternative, “<… Class=”onsite”>” may be used to indicate links that are known to be appropriate for seamless transition. With the use of this approach, browsers should implement the “offsite” action for links that do not include this attribute.
