No - there have been plenty of teams with 8-8 records in the playoffs, but no team with a losing record has yet made it in.
Update:On 1-2-11, the Seattle Seahawks became the first 7-9 team in NFL history to win their division and make the playoffs.Yes. The 1970 Cincinnati Bengals rebounded from a 1-6 record to win their last seven games and qualify for the AFC playoffs. They lost in the first round of the playoffs to John Unitas and the Baltimore Colts, who went on to win Super Bowl V.
As of the 2011/2012 NHL season no team has gone 16-0 in the playoffs.
No the 2001 playoff Lakers went 15-1 in the playoffs only loss was the first game of the finals.
2002 New York Jets
The 2010 Seattle Seahawks made the playoffs by winning the NFC West Division Championship with a record of 7(wins)-9(losses). They qualified by beating the St. Louis Rams in the last game of the regular season.
It varies depending on the standings of the teams that are positioned to get into the playoffs. The top eight teams from each conference get in, but the number of wins that have gotten teams to the playoffs go from as low as around 36 wins to being as high as 72 wins. Any NBA team that wants to qualify for the playoffs has to finish with a better record than the team holding eighth place in their conference.
no it has never happened
Ravens
celtics
Since the NFL went to it's current twelve game playoff format in 1990 eleven team who have been three games below .500 at any point during the regular season have gone on to make the playoffs. The last team to start the season 1-4 and make the playoffs were the 2002 NY Jets who not only made the playoffs but won the AFCE. The 2008 Chargers are the only team since 1990 to ever be four games below .500 at any point during the regular season and make the playoffs. SD won the AFCW in a tie breaker with the Denver Broncos.
san Diego in 1992
Between the 2000-2009 seasons, no team has made the playoffs every season. The Indianapolis Colts have made the playoffs in 9 seasons, the most of any team. 2001 was the only season in the past 10 that they didn't make the playoffs as their record was 6-10. The Philadelphia Eagles made the playoffs in 8 of those 10 seasons, missing out only in 2005 (6-10) and 2007 (8-8).