Christina Aguilera fluffed a line of the Star-Spangled banner as she belted out a version of the US national anthem to open Sunday's Super Bowl in Texas.The singer, 30, should have sung: "O'er the ramparts we watched, were so gallantly streaming?" but repeated an earlier line with a slight variation.She sang: "What so proudly we watched at the twilight's last gleaming."The anthem is one of the set piece events of the glittering Super Bowl pre-game ceremony.Aguilera's mistake immediately set social networks abuzz with chatter. Her representative could not immediately be reached for comment.ControversyThe NFL final - which was this year contested by the Green Bay Packers and the Pittsburgh Steelers - is one of the most-watched programmes in US television.Last year it drew a record 106.5 million viewers.The half-time show of Super Bowl in 2004 created controversy when Justin Timberlake ripped a piece of Janet Jackson's top, resulting in a glimpse of her right breast.The pair said the incident was accidental, calling it a "wardrobe malfunction", but broadcaster CBS TV was fined $550,000 (£351,000) after hundreds of complaints from viewers.The fine was subsequently revoked in July 2008.Source: BBC