どこ だか ドア

「 the secret door（ザ・シークレット・ドア） 」は、“世界のどこか”に連れて行ってくれるマジカルなサイト. I think its some sort of informal way to say it.|i would translate どこだか？ just as the informal question where is it doko= wo da= informal form of desu ka= marking a question english (us) french (france) german italian japanese korean polish portuguese (brazil) portuguese (portugal) russian simplified chinese (china) spanish (mexico) traditional. Isn't the door in doraemon called どこだかドア？ could be a reference to that, because だか is not allowed to use as casual of ですか i think.