Follow this link to see the chart.
The New Orleans Saints have a notoriously bad history, but from the mid 2000s up until 2011, they've seen a very real change of fortune. These events may coincide with the additions of Sean Payton and Drew Brees in 2006, but who's to say. According to the graph, the Saints' best moment in their history (better than Porter's pick off of Favre, and even better than winning Super Bowl XLIV) was defeating the Atlanta Falcons in Week 13 in 2009 to go 13-0. Since 2012 (read: Bountygate), the Saints have seen a downturn, but hope still remains to right the ship in the coming seasons.
If you'd like to know about Elo itself, here's the description from the site. To know more about how it's evaluated, follow the link in the block quote, and be sure to vote in the poll below on your favorite moment in team history:
Elo is set so that an average NFL team has a rating of about 1500, although the league average can be slightly higher or lower, depending on how recently the league has expanded â expansion teams start with a rating of 1300. You can read more about our methodology here; all game results are from Pro-Football-Reference.com. "Championships" include Super Bowl wins and pro league titles from before the Super Bowl era, including the winners of the National Football League, American Football League, and American Professional Football Association (but excluding those of the All-America Football Conference). There are over 90 defunct franchises in pro football history, but only those that played at least 40 games can be selected above.