JSFiddle - React, Tailwind, and code Playground

HTML

<div id="sidebar"></div>
<div id="content">
    <div id="clearer">clearer</div>
    </div>

CSS

#sidebar { height:500px; border:1px solid red; float:left; width:100px; }
#content {
    float:left;
    width:200px;
}
#content #clearer {
    clear:both; zoom:1;
}