JSFiddle - React, Tailwind, and code Playground

HTML

<div id="wrap">
    <div class="sideL">проверка</div>
    <div class="middleBlock"> текст</div>
    <p class="deFloat"></p>
    <footer>
        <p>подвал</p>
    </footer>
</div>

CSS

* {
    margin: 0;
    padding: 0;
    font-size: 100%;
}
html, body {
    height: 100%;
}
.deFloat {
    clear: both;
}
#wrap {
    margin: 0 auto;
    width: 100%;
    min-width: 500px;
    min-height: 450px;
    height: 100%;
    font-family: sans-serif;
    background: #eaeaea;
}
.sideL {
    width: 200px;
    height: 100%;
    background: #353535;
    float: left;
}
footer {
    width:100%;
    height: 30px;
    background: #000;
    color: #eaeaea;
    text-align: center;
}
.middleBlock {
    margin: 0 auto;
    width: 300px;
    height: 300px;
    background: red;
    border: 2px solid black;
}