RAMALLAH, WEST BANK - MAY 15: A Palestinian demonstrator throws back a tear gas granade towards ISraeli soldiers, during clashes with Israeli soldiers at Qalandiya checkpoint near Ramallah, West Bank , Sunday May 15, 2011. Today Palestinians mark the 63rd anniversary of "Nakba", Arabic for "Catastrophe", the term used to mark the events leading to Israel's founding in 1948. Photo by Gili Yaari