Yom Kippur is one of the most sacred days in the Jewish calendar. Jews fast, pray, reflect and seek forgiveness for their sins over the past year. Jews devote the entire day to G-d, refraining from work, food and sexual relations. We wish anyone remembering this day, a very blessed Yom Kippur, along with the mercy and forgiveness of G-d.
For more info: http://www.jewishvirtuallibrary.org/jsource/Judaism/holiday4.html