Facebook founder Mark Zuckerberg said the social networking site's News Feed "is one of the most important things we have built", ahead of an expected revamp to the service.
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Joshua Clements stabbed two 19-year-olds while 4,000 people were gathered at the royal park.
The vessel was spotted off the Kent coast at around 5.40am on Thursday.
The US secretary of state called for a new approach to resume talks amid the civil war, including unity government and transfer of weapons.