box-sizing属性可以为三个值之一：content-box（default），border-box，padding-box。

content-box，border和padding不计算入width之内

padding-box，padding计算入width内

border-box，border和padding计算入width之内，其实就是怪异模式了~

ie8+浏览器支持content-box和border-box；

ff则支持全部三个值。

使用时：

-webkit-box-sizing: 100px; // for ios-safari, android

-moz-box-sizing:100px; //for ff

box-sizing:100px; //for other

<style type="text/css">

    .content-box{

        box-sizing:content-box;

        -moz-box-sizing:content-box;

        width: 100px;

        height: 100px;

        padding: 20px;

        border: 5px solid #E6A43F;

        background: blue;

    }

    .padding-box{

        box-sizing:padding-box;

        -moz-box-sizing:padding-box;

        width: 100px;

        height: 100px;

        padding: 20px;

        border: 5px solid #;

        background: red;

    }

    .border-box{

        box-sizing:border-box;

        -moz-box-sizing:border-box;

        width: 100px;

        height: 100px;

        padding: 20px;

        border: 5px solid #3DA3EF;

        background: yellow;

    }

</style>

aaarticlea/png;base64,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" alt="" />