A margin three-quarters of an inch in width should be left, on the
side of the letter, as shown in the diagram. This is convenient for
any mark or memorandum which your correspondent may desire to make
concerning anything contained in the letter, but its greater value
lies in the open, airy, and cheerful dress which it imparts to the
letter. A margin too narrow conveys the idea of stinginess, as if to
economize paper, while an irregular or zigzag margin conveys the idea
of carelessness or want of precision. On a sheet of note paper the
margin may be only one-half inch in width, thus making its width
proportionate to the size of the sheet.