Here's the site: Day of Silence. Due to the event being tomorrow, at some points the server may be down due to too much traffic.
Also, to anyone who decides they want to participate, this is perhaps the most important thing to remember:
Please note that schools are NOT allowed to forbid you from taking part in the event (although if a teacher calls on you in class you must answer the question). The site has a legal form you can show to the school.