Factual error: The season 5 episode "Designated Target" deals with the murder of a Navy admiral and the cab driver transporting him through Rock Creek Park in Washington, DC. Late in the episode, the investigators try to get a lead on another cab driver by tapping into the records from taxi meters. The problem is, DC cabs don't yet have meters. Congress banned them in 1933, but legislation passed this year now gives the DC government authority to install meters. And in fact, just days before this episode aired in Nov 2007, DC's mayor announced plans to switch from the zone system to meters by April 2008.
Continuity mistake: When Gibbs comes to Abbie's lab to inquire about the smoke detector and computer, the CPU is disassembled on her lab table with the "hard drive" sitting on a white tray that is positioned in front of the computer cover that has been removed from the CPU. The "hard drive" is white colored. At the cut to a close up of the hard drive it is now black and a completely different piece, the white tray has disappeared and the hard drive is sitting on the CPU cover. When it cuts back to the wide shot the white try has returned and the hard drive is back to the original white.
Revealing mistake: During season 4 the same television clip of President Bush and VP Cheney disembarking Air Force One is used on the background television in the squad room. In some cases the clip is running and not in unison, on three of the televisions in the same scene from shot to shot.