Actress Katrina Kaif, who turned 33 on Saturday made her social media debut by joining 'Facebook' on the occasion of her birthday. Katrina also hosted a birthday party, which was attended by Bollywood celebrities including Alia Bhatt, Sidharth Malhotra, Karan Johar and Arjun Kapoor. Katrina, who made her Bollywood debut in the 2003 film 'Boom', features among Bollywood's highest-paid actresses.