It is so hated that its use is illegal in Germany and several other countries, even in countries where it is legal it is highly offensive and associated with neo-Nazis and other extremists.
In Nazi Germany all citizens were forced to use this salute in everyday life, even children were continually bombarded with it as a form of brainwashing. The now infamous motto of "Heil Hitler" was expected when performing the act. "Sieg heil" was also often said.
Due to being illegal in several countries and generally hated in countries where it is legal neo-Nazis have come up with new ways to make a "Hitler Salute" - one of the more inventive forms is a written code of "88" amongst neo-Nazis, which stands for "Heil Hitler" (H being the eight letter of the alphabet). It is commonly used in conjunction with the Fourteen Words, with "14/88" being a common white supremacist slogan.
The "Hitler Salute" has also become a part of Football Hooligan culture in Europe.