WSN includes facilities to check for dead links, check for duplicate links, check for link partners who aren't reciprocating, and check for sites with undesirable content. These options are in the left side admin panel menu under "Listings" when you have the link checkers switch activated.

The checkers list suspects and prompt you to decide what to do with them. An explanation of what you can do to suspects is in the suspect links article.

The duplicate checker simply finds instances where you have multiple copies of the same link. See the more detailed duplicate link checker article.

The reciprocal checker searches for your directory url, site url (as listed at Admin -> Settings -> System Configuration), an in.php link to your directory, or whatever the "reciprocated with" field contains. See the more detailed reciprocal link checker article.

The dead link checker simply determines whether the site is accessible. See the more detailed dead link checker article.

The content checker allows you to specify undesired phrases which, if found on the site, will cause it to be flagged for you. This can be helpful in identifying websites that've been bought up by spammers, domain placeholder pages or undesired pornography sites.

See the troubleshooting article for link checkers if you encounter problems.