Although acquainted somewhat with taboo numbers and avoidance of certain addresses, I hadn’t seen it in practice—admittedly applying my own form of lore and arithromania to disbursements when paying bills and try to have a figure four in there albeit mindful that auspicious dates, versions can deceive—and enjoyed this enlightening overview from Language Log in the form of a superstitious elevator panel, removing the fourth storeys as a homophone for death (死, sì, sĭ), or more specifically according to the Eighteen Level of Hell in Chinese mythology, as elaborated in Journey to the West, the association with the Mirror of Retribution, the literal “evil mirror platform” (孽鏡臺)—accounting for further omissions for those wanting to bypass the degrees of purgatory awaiting the ones dodging dharmic-for-karmic justice in this life. Much more at the links above.