A faux pas, (French for false step) is a violation of accepted, although unwritten, social rules. Faux pas vary widely from culture to culture and what is considered good manners in one culture can be considered a faux pas in another. For example, in English-speaking Western countries it is usually considered good manners to bring a bottle of wine when coming to someone's house for dinner. In France, however, this is considered insulting as it suggests the hosts are unable to provide their own good wine. However, bringing flowers to the hostess is never a faux pas, although you sometimes need to be careful which kind of flowers you bring.
Origin of term
The term comes from French and literally means "false step". However, it is a formal rather than everyday expression in French and does not generally have the figurative meaning used in English. It is occasionally employed to describe a physical loss of balance or general mistakes (for instance: mes faux pas dans la vie, the mistakes I made in my life). If you use faux pas with the English meaning in France, people might think you are making a slight grammatical mistake with faut pas, the colloquial pronunciation of il ne faut pas, meaning must not in English. For faux pas with the English meaning, the French would usually say gaffe or erreur.
Examples
African regions: A right-handed handshake.
Arab countries; Indian Subcontinent; Middle East ;South-East Asia: Displaying the soles of your feet or touching somebody with your shoes.
China: Giving someone a timepiece as a gift. Traditional superstitions regard this as counting the seconds to the recipient's death. Another possible interpretation of this is that the phrase "to give clock" in Chinese is "song zhong," which is a homophone of a phrase for "attending a funeral."
Central Europe: Shaking hands while wearing gloves (this does not apply to women).
France: Asking for cheese after taking dessert.
Japan: When greeting or thanking another person, not bowing lower than the other person when the other person is older than you or has a higher social status.
Romania; Russia; Slovakia; Czech Republic; Hungary; Serbia: Giving somebody an even number of flowers. This should only be done in funerals.
Scandinavia: Being late. The Nordic countries are unusually punctual, with meetings, events, and public transport usually happening on time.
Thailand: Stepping over or standing on bills or coinsthey all have the face of the King, who is highly revered.
Turkey: Addressing someone older than you or higher in social status with his/her bare name. Adjectives like uncle/aunt, (elder) brother/sister or formally Mr./Mrs. is expected to be used.
United Kingdom: Signifying "two" of something by holding up two fingers with the back of the hand pointed towards the listener can be mistaken for an offensive gesture (similar to the finger). Holding up two fingers with the hand held the other way (palm of the hand towards the listener) is perfectly acceptable.
United States: Not leaving a proper tip or gratuity for a waiter at a restaurant. While some establishments in other countries may add a gratuity to the bill, in the US this is not usually done and is left up to the patron to leave an adequate tip depending on the quality of service. Tips for average service range anywhere from 15-20% of the final charges.