稍后完善
http://www.cnblogs.com/trlanfeng/archive/2012/11/04/2753280.html
http://www.cnblogs.com/asqq/archive/2012/04/19/2456927.html
http://www.open-open.com/lib/view/open1420120422531.html
http://www.cnblogs.com/Tzhibin/archive/2015/04/12/4420537.html
页面上clientTop,offsetTop,scrollTop的理解，js元素的event.x/.clientX等位置的理解
原文：http://www.cnblogs.com/coconutGirl/p/7728111.html