Vertical Rhythm on the Web
"Space in typography is like time in music. It is infinitely divisible, but a few proportional intervals can be much more useful than a limitless choice of arbitrary quantities." So says the typographer Robert Bringhurst, and just as regular use of time provides rhythm in music, so regular use of space provides rhythm in typography, and without rhythm the listener, or the reader, becomes disorientated and lost.
Read the full article on 24ways.org.