fú dào le hé fú dào le xiéyīn, suǒyǐ yǒurén bǎ fúzì dàozhe tiē

“福倒了”和“福到了”谐音，所以有人把福字倒着贴。

"Fortune upside down" and "fortune has arrived" are homophones, which is why some people paste the character "Fu" upside down.