FILE - Britain's Queen Elizabeth II arrives at television studios, in Belfast, Northern Ireland, in this Oct. 21, 2010 file photo. Britain's Queen Elizabeth II is launching an official Facebook page, offering fans daily updates on her engagements, the royal household said Sunday Nov. 7, 2010. (AP Photo/Peter Morrison, File)
March 7, 2012 7:52:35 AM PST
LONDON (AP) - March 7, 2012 --
Britain should pay tribute to Queen Elizabeth II's "unerring grace, dignity and decency" as she marks 60 years on the throne, Prime Minister David Cameron said Wednesday in a rare tribute at Parliament.