For the first time, the Chesapeake Group documented the year of capture for all of the URLs in our 2012 sample. Not surprisingly, the data show that a URL’s risk for link rot increases with time; 40 percent of URLs captured in 2007 have succumbed to link rot, while all of the materials captured in the first few months of 2012 remain at their original web addresses.
Dead links are a nightmares for everyone who writes (and read) online, too many times i found myself reading a quote in a page pointing to an external article just to find it down.
Ofttimes times those errors are not due to a removal of the site, but to it’s just bene moved. Maybe he changed the URL and he forgot to issue a - 301 - Redirect.
The solution i found is, apart from using the great Web Archive, to save my favourite articles to Pinboard which stores your favourite articles offline if you buy an archival account.