JSFiddle - React, Tailwind, and code Playground

HTML

<div id='col-container'>
    <div id='right-col'></div>
    <div id='content-col'></div>    
</div>

CSS

#col-container {
 background: blue;
 /*height: 500px;*/
 width: 600px; 
}

#col-container:after {
 content: ".";
 display: block;
 clear: both;
 height:0;
 visibility: hidden;
}

#right-col {
 background: red;
 width: 100px;
 float: right;
 height: 150px;
}

#content-col {
 background: yellow;
 margin-right: 100px;
 height: 180px;
}