box sizing

* {
  -webkit-box-sizing: border-box;
     -moz-box-sizing: border-box;
       -o-box-sizing: border-box;
          box-sizing: border-box;
}

使用时去除星号前的符号，github显示星号有点问题
使用上述样式后，所有元素无需再计算margin、padding、border带来的宽度影响，支持IE8+
http://caniuse.com/#search=box-sizing

Known issue:
1. Android browsers do not calculate correctly the dimensions (width and height) of the HTML select element.
2. Safari 6.0.x does not use box-sizing on elements with display: table;
3. IE9 will subtract the width of the scrollbar to the width of the element when set to position: absolute, overflow: auto / overflow-y: scroll