At Admin Panel -> Settings -> Switches, the "Link checkers" switch enables utilites to check for dead, non-reciprocating and duplicate links as well as undesirable content. This is normally only applicable to WSN Links, not the other scripts, though you could use it anywhere you have the URLs switch on. The link checkers are located in the Admin Panel's "Links" menu.

From time to time you may wish to cull dead sites from your directory. The dead link checker cycles through trying to load each site, and if it cannot do so it marks the link as suspect so that you can manually verify that the link does not work and decide what action to take. Sometimes a site is down temporarily and returns, so you may wish to wait until a site has been marked suspect several times before taking action.