Paul Irish blogs here: http://www.paulirish.com/2012/box-sizing-border-box-ftw/ that a CSS3 feature promises to end the foolish layout war between those who think box boundaries should be measured to the borders and those who think a box’s boundaries are the size of its content. This has been a headache for anyone trying to get a set of boxes to line up properly and to work across all browsers, especially Internet Explorer.
Vijay Sharma shares his insights here: http://crypt.codemancers.com/posts/2013-11-17-box-model-behaviour/
Credit to: html5weekly.com (now merged into Front End Focus)