CSS line-height

http://www.zhangxinxu.com/wordpress/2009/11/css%e8%a1%8c%e9%ab%98line-height%e7%9a%84%e4%b8%80%e4%ba%9b%e6%b7%b1%e5%85%a5%e7%90%86%e8%a7%a3%e5%8f%8a%e5%ba%94%e7%94%a8/