[Colin F]

Looking at the site bradolson mentioned:

The day after Thanksgiving in the United States, is frequently referred to as Black Friday. One of the major U.S. holiday shopping days, it is the day many U.S. consumers begin Christmas shopping. The day is heavily promoted by retailers. The origin of Black Friday comes from the shift to profitability during the holiday season. Black Friday was when retailers went from being unprofitable, or "in the red," to being profitable, or "in the black", at a time when accounting records were kept by hand and red indicated loss and black profit.

Last year, Black Friday was a huge day for internet retailers. Amazon.com received 2.5 times as many orders between midnight and noon as it did the same time a year ago, according to company spokesman Paul Capelli. Many other Internet retailers also saw a huge spike in sales as customers jumped online instead of into their cars. This year figures to be just as lucrative, if not more.