The man who created the World Wide Web, Sir Tim Berners-Lee, has warned of the dangers of the Internet. He described his three main worries about how the Internet is being misused.
The first problem is fake news. He said websites and companies are creating fake news just to make money, or to try and change people's political opinions. He said the danger is that fake news "spreads like wildfire".
The second problem is political advertising. He said adverts are used in "unethical ways" to stop voters from voting or to make them click on fake news stories.
His final concern is the misuse of personal data by governments. He said people are killed in some countries because of the websites they visit.
Berners-Lee invented the web in 1989. He said that it had "lived up to [his] vision" in many ways. He said:"I imagined the web as an open platform that would allow everyone, everywhere to share information, access opportunities and collaborate across geographic and cultural boundaries."
His letter outlined a five-year strategy to keep his vision alive. He said there were complex problems, and that the solutions would not be simple. He wants to put, "a fair level of data control back in the hands of people".
He also wants to stop governments from looking at our online data, which he said creates a "chilling effect on free speech". And he wants to fight against fake news and misinformation. He called on all Internet users to help.