Busted links are the scourge of anyone who runs a web site.
Outside links change so quickly that keeping your site up to date is damn near impossible. If you have a small web site then checking each link by hand isn't to bad, but if it's a little larger then good luck. What you really need is a HTML link checker like LinkBot to do all the scrub work for you. Just fire up Linkbot, tell it where to begin and it's off and running. You can give Linkbot a starting URL and it will check everything below it, or you can selectively filter out what Linkbot will and won't check on your site.