1) The 1.3 number is setting the line-height, in shorthand.
2) It’s only supported in IE and Opera, but it means that at the end of a paragraph block, for example, there can never be just one lonely word, it will at least pull down another word from the line before it. Just good typography.
3) Also good typography. See: http://www.aestheticallyloyal.com/publi … egibility/ Although there are some potential drawbacks… I may post about that soon as I learn more.