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8 August 2013 Last updated at 21:53 BST

Several companies have pulled adverts from the website, after the death of a teenager who was bullied online.

The father of 14-year-old Hannah Smith from Leicestershire said she killed herself after being targeted on where she faced anonymous taunts and comments urging her to end her life.

The BBC's Clive Myrie explains how the social media website works.