Content-box-mode

by Reusablecode

HTML

<div class="left">content-box</div>
<div class="right">box-sizing</div>

CSS

.left{
    float: left;
    width: 30%;
    background-color: pink;
    //border: 3px red dotted;
    height: 150px;
}
.right{
    float: left;
    background-color: lightgreen;
    width: 70%;
    //border: 3px green dotted;
    height: 150px;
}