It's kind of a strange when you think about it, but rudeness is 100 percent a cultural construct. Anything that you can think of that's considered rude might be seen as perfectly fine in another place.
What you have to apologize for varies from culture to culture. The key, of course, is knowing what's acceptable where you happen to be. So before you head out on your next trip, check out what the local customs are. Here are a few of some of the most common taboos from around the world.