For 2009 the answer was the Detroit Lions (2-30 for two seasons) and the St. Louis Rams (1-15 for one season). The newest team, the Houston Texans, had a franchise record of 49-79 (2002-2009).
However, by 2011 both the Lions and Texans had vastly improved, and the weakest teams appeared to include the Rams, the Miami Dolphins, and the Indianapolis Colts who were without Peyton Manning (in his 13th year). Both teams did better in 2012.
In 2012, the worst record belonged to two AFC teams: the Jacksonville Jaguars and the Kansas City Chiefs.
(see discussion for previous answer)
tennessee titans
The Detroit Lions.
washington redskins
Bad offense They won super-bowl XLIV, maybe?
The Cleveland Browns. They are also the worst team because they don't have any good players.
bears
There is not a chance in the whole world that the best college team beat the worst NFL team!
Lions
A combination of poor performance, lack of talent, and ineffective coaching can make a team be considered the worst in the NFL.
The Detroit Lions currently hold the worst record in the NFL.
The Detroit Lions currently hold the worst record in the NFL.
As of November '09 the St. Louis Rams are the worst team.
Cleveland Browns, and BENGALS
The NFL team with the worst overall record in 2008 was the Detroit Lions, who were 0-16.
The Detroit Lions currently hold the worst record in the NFL.
The Detroit Lions hold the title for the worst record in the NFL.
As of now, the Detroit Lions are considered one of the worst teams in the NFL.