E404 was supposed to be a European B class road in Belgium, connecting the cities Jabbeke and Zeebrugge. However, the road was not built according to the original plans. The number is nevertheless still given to a route between the two cities as a likely Easter egg referencing a HTTP response code 404 "Not Found", but it is not signposted on any existing roads between those cities nor found on maps.
Route
E40 Jabbeke E34, E403 Zeebrugge
References
External links UN Economic Commission for Europe: Overall Map of E-road Network (2007) European Agreement on Main International Traffic Arteries (AGR) : consolidated text of the AGR (1999, page 20)