Holocaust
The Holocaust (Also known as Ha-Shoah) refers to a series of programs of National Socialist Germany during the Second World War involving the mass killings of eleven Million "undersirables", most notably that of six million Jews, in acordance to Nazi Racial Ideology.
Holocaust Denial
A small number of White Supremacists and anti-Semites claim that the Holocaust never happened as a means of keeping face and trying to convince others that they are not a bunch of small-minded, hate-filled barbarians. Such claims fly in the face of mountains of evidence including documents, sights, mass graves, the major decline of the Jewish population (particularly the near complete destruction of Poland's Jewish population of three million) of Europe and so on. The near extermination of the Polish Jews and east European Roma (aka "Gypsy") population is just one more nail in the denier's coffin.