According to Braingle, the answer to the riddle, "What has four legs but only one foot?" is "A bed." The confusion in the riddle lies in the English language conventions for naming parts of animate and inanimate objects.
When talking about an animal, a leg is an ambulatory appendage ending in a foot. Inanimate objects, like chairs, are said to have 'legs', but they are rarely said to have separate 'feet'. Furthermore, a bed has both a 'head end' and a 'foot end', as seen in the Efi-Costarica.com Antique Furniture Guide. Therefore, taking into account a bed's four 'feet' and its 'foot end', it fits the riddle's conditions.