Level 404 is the 7th game and 405th level. Level 404 resembles a simulated world that appears to have some visual problems with gray landscape, squares and cyllinders. Level 404 otherwise doesn't contain much exept for glitches that slow you down with a drowsiness effect on the character that makes him look dizzy and slightly confused. There are no listed entrances in any game but you exit via a no-clip spot that leads to Level !.
Level 404, aformentioned squares and cyllinders visible along with a glitch area and a no-clip spot.