JSFiddle - React, Tailwind, and code Playground

HTML

<div class="site">
    <div class="content">content</div>
    <div class="ads left">ads-left</div>
    <div class="ads right">ads-right</div>
</div>

CSS

.site {
    width: 500px;
    margin: 30px auto;
    position: relative;
}

.content {
    background: yellow;
    height: 100px;
}

.ads {
    background: red;
    position: absolute;
    top: 0;
    width: 200px;
    height: 50px;
}

.right { left: 100%; }
.left { right: 100%; }