The homonym of 404 contains two fours, four is one thing, and two fours are everything. Everything goes well means everything goes well.
Many people are superstitious about numbers. They think that the number 8 always represents good luck, while the number 4 that sounds like "death" should be avoided, and they will prefer some lucky numbers. In fact, the room number 404 mainly depends on whether you are taboo or not, and there is nothing wrong with not being taboo.