Almost everyday you see a 404 error or Not found message while surfing the Internet. This error occurs when your computer is not able to communicate with a server or server can't find what was requested. Since the decimal form of April 4 coincides with 404, this day has become 404 Day.
The UN General Assembly declared that April 4 is an annual observation of International Day of Landmine and Assistance. This International Day was created in 2005 and its first observation took place in 2006.