It may mean you have a link in your code that’s not attached to any text. This sometimes happens when an editor changes a link destination without first “un-linking” the original. (ie. the contact person for something changed, so you switched to the new person’s email address). This can leave some residual code that you can’t see, but assistive technology can. See: Fixing “phantom links”. If you need help locating and removing it from your site’s code, contact your developer.