How many bookmarks do you have in your browser? I use Firefox as my primary browser, and Opera as secondary. But still both of them have more 200 bookmarks each. Even IE has some old collection of bookmarks saved in it. None of us ever bother to check dead bookmarks and delete them. It sure is a tedeous job!
AM-DeadLink is a freeware that detects dead links and duplicates in browser bookmarks and text files. If a bookmark has become unavailable you can verify and delete it permanently. Additionally you can download favicons for all your Favorites and Bookmarks.