JSFiddle - React, Tailwind, and code Playground

HTML

<div id="header">
    HEADER
</div>
<div id="middle">
    <div class="left">
        LEFT
    </div>
    <div class="right">
        RIGHT
    </div>
    <div class="clear">
    </div>
</div>
<div id="footer">
    FOOTER
</div>

CSS

body, html {
    margin: 0;
    padding: 0;
}

#header,
#footer {
    height: 100px;
    background-color: #444;
    color: white;
    text-align: center;
    padding: 30px 0px;
    box-sizing: border-box;
}

#footer {background-color: black;}

#middle {
    height: calc(100vh - 200px);
}

#middle .left {
    float: left;
    height: 100%;
    width: 200px;
    background-color: #ccc;
}

#middle .right {
    float: left;
    height: 100%;
    width: calc(100% - 200px);
    background-color: #777;
}

.clear {
    clear: both;
}