This tag referes to the ASCII-art "uso desu" (ウソです) which means "it's a lie,"and is used in2channel, Japanese biggest BBS.The AA is as following*      *＊  ウソです  ＋n ∧＿∧ n＋ (ﾖ（* ´∀｀）E)Y     Y    ＊and used to completely deny all text written in the 1st comment of the boring thread (mainly in 2nd comment.) Additionally, it is a kind of manner in 2ch to write "A lie, I see" (なんだうそか) immediately if you see this AA.
uso desu