Link checker modules fails to detect a test broken link
Found Link checker works after  'run cron'

-- Found in video: https://www.youtube.com/watch?v=Hcl9iwIFZ2k
That a cron job has to be run after the configuring.
--  I had already set for automatic running of cron job.  For some reason it didn't work.
--  It worked after running cron job manually.
site-url/cron.php for D5 and D6

-- OR For Drupal 6.x, see in your site: Administer > Reports > Status report > Cron maintenance tasks > Run cron manually.  

Steps for checking links:


Make sure link checker configuration is what you want  
http://site-url/cron.php  in browser to run cron job (it yields blank page after the run)  
See report for broken links and follow up specific links.  


Here is another link for some relevant info on link checker module:
http://www.lullabot.com/blog/article/module-monday-link-checker