Sometimes, webmasters who provide a link back to your site will remove it after a period of time. To be sure you detect this and rank their link accordingly, you can run the reciprocal link checker.

The reciprocal link checker checks the page which is listed as the reciprocal link URL for the link. Submitters should have provided this info at the time of submission, presumably, but you can edit the link to alter the reciprocal URL. When that page is grabbed, it's searched for any instance of your website's URL -- thus you must be sure that you have entered your website's URL on your 'manage settings' page in the 'system settings' area.

If a particular site uses a non-standard URL to link back to you, perhaps a dynamic link code such as out.php?id=123, then you can edit this special link into that links information. When editing the link, find the "Reciprocated with" field and provide the URL which they use to link to you.