Typography and Page Layout: Margins
http://www.typography-1st.com/typo/margins.shtml

Magnik, John
Typography First

Abstract:

Margins are the imaginary vertical demarcations for text or tabular columns. Overall or primary margins are established by the line length function or the cumulative total of secondary margins (tab or text columns). Establishing margins requires careful consideration. The amount of white space surrounding printed material effects both appearance and the readability of the page. Plenty of marginal space indicates luxury or formality; small margins indicate commercialism.