One April Fools' Day prank that has provoked a strong reaction is YouTube's claim that it is planning to stop accepting video uploads.
In a video addressed to users, a YouTube employee announces that the entire website was an attempt to "find the best video in the world" and that the company will spend the next decade reviewing all of the entries to pick a winner.
One user commented on the video "I almost had a heart attack ... That wasn't funny," while another expressed their dismay at having to "wait a whole 10 years" for the winner to be announced.
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Mladic, now 75, was the military commander of Bosnian Serb forces in the 1990s, who fought against the Bosnian Croat and Bosniak armies.
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His representatives said Cassidy, who was hospitalised last week, died "surrounded by those he loved."