春节贴“福”字，为什么要贴倒？

The Chinese character “fu” means good fortune and happiness, and during Spring Festival virtually every family would paste it upside down on their doors in the hope that the word could bring blessings to their families. As to why “fu” should be placed upside down there are three interpretations.
中国汉字“福”意味着好运和幸福。每到春节，几乎每个家庭都会将“福”字倒贴在家里的门上，以希望这个字能给家人带来祝福。为什么“福”字要倒着贴呢？这里有三种解释。

The first interpretation has the practice of pasting “fu” during Spring Festival originate in Jiang Ziya of the Zhou Dynasty (11th Century-256 B.C.). When Jiang Ziya was made a god, his wife demanded to be made a goddess. “After I married you I was always in poverty in my life,” Lord Jiang said. “It seems you are destined to be poor. So let me appoint you as the Goddess of Poverty.”
第一种关于春节贴“福”字的习俗跟周朝（公元前11世纪－前256年）的姜子牙有关。姜子牙成仙以后，他的妻子请求姜子牙将她封仙，“自从我们成亲以后，我一直过得很困苦。”姜子牙说道，“似乎你命中注定就该贫穷，所以我封你为‘穷神’。”

No knowing what being the Goddess of Poverty held in store for her, his wife was nevertheless happy about becoming a goddess. Cheerfully, she asked, “Now that I'm the Goddess of Poverty, where shall be my domain?” Jiang replied, “You are off limits wherever there is good fortune” When the residents got word of Jiang's instruction, they wrote the character “fu” on paper and pasted it on the doors and windows of their houses to keep the Goddess of Poverty away. Thus pasting “fu” during the Spring Festival became a Chinese tradition.
虽然不知道‘穷神’意味着什么，他的妻子还是很高兴能被封神。她高兴地问道：“既然我已经被封为‘穷神’，那我该管辖哪里呢？”姜子牙答道：“有好运的地方你都禁止踏入。”居民们听到姜子牙的指示，就在纸上写下“福”字贴在家里的窗户上以赶走“穷神”。久而久之，春节贴“福”字就成了一种传统。