JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE HTML>
<html>
<body>

<div class="main_container">

    <div class="left_container">
    </div>

    <div class="right_container">
    </div>

</div>

</body>
</html>

CSS

div.main_container {
    background: #000; 
    border: none;
    -moz-border-radius: 15px;
    -webkit-border-radius: 15px;
    -khtml-border-radius: 15px;
    border-radius: 15px;
    width: 100%;
    min-height: 400px;
    margin: auto;
}

div.left_container {
    float:left;
    position:absolute;
    width: 220px;
    background: red;
    margin: 0;
    min-height: 100%;
    padding: 0;
}

div.right_container {
    position: relative;
    margin-left: 220px;
    width: 715px;
    height: 100px;
    background: blue;
}