This is the number of attempts the application will make before it actually flags the listing as a dead link. That is, if set at 3 the application will make 3 attempts to look for an active website before it determines that it's a dead link. You should leave this at 3 attempts to ensure that the listing owner’s website was not simply experiencing unexpected downtime when the application was checking their website. Of course, the higher you make this setting, the longer the URL Validation process will take.