Forum Moderators: martinibuster
If it's possible to determine where the user was trying to go (e.g. after a site redesign or if inbound-link typos have been found), redirect the user to the correct page seamlessly. If it's NOT possible, then show the user a custom 404 page which can be supplemented with whatever information or navigation you wish (not AdSense, though).
5. Prohibited Uses. You shall not, and shall not authorize or encourage any third party to: (v) display any Ad(s), Link(s), or Referral Button(s) on any error page...