I've been collecting web bookmarks for well over 15 years. If you're anything like me, your bookmark list has grown out of control. I tend to add links with software I want to find again, or which discusses an interesting topic, or simply something I was part-way through reading and wanted to come back to later and finish. I add quite freely, but rarely go back and clean things up. And I NEVER go through and verify how many of those links still work, even though some of them were added over a decade ago.
Today, I use Xmarks to keep my bookmarks in sync across browsers and across computers. If you don't use Xmarks, I recommend you do. Even if you only have one computer, it's a great way to keep your bookmarks backed up. I hereby openly invite Xmarks to implement a link checking feature, providing users the option to remove dead and duplicated links. I also invite them to explore social bookmarking, but I digress - this is really about removing dead links.
So Xmarks doesn't do link checking today, but AM-DeadLink does. Unfortunately there is no Mac version, but it does support all of the major browsers. And for Internet Explorer it will also download the current favicons. So here's a nifty way to filter out dead and duplicate links from your bookmarks (1168 in my case), regardless of where they are now...
How many errors did you have? Out of 1168 bookmarks, I had about 190 errors, plus a little over 200 redirects, plus 8 links duplicated and triplicated into 22.
Special note to those of you in censored countries - some errors may be caused by your country's filters, not by a problem with the site itself.