I spent my morning going through all of the outbound links on an old, established site checking for sites that no longer exist and sites that have been banned. Because this is an older site, it has no automated process built in for checking these things. Because it is such a time-consuming process to check each link, I have put it off for far too long. There were numerous instances of bad links, which I promptly deleted. There were even a couple of links to sites that look as though they may have been banned from Google. Linking to those sites could result in a penalty to me for linking to "bad neighborhoods". Those links got deleted quickly! As tedious as manual link-checking can be, it is important to remember to keep up with it as often as possible. Otherwise, you may be linking to sites that were once ok, but are now non-existant or banned.