JSFiddle - React, Tailwind, and code Playground

HTML

<div id="main-content">
    <div id="left-column">
        LEFT
    </div>
    
    <div id="right-column">
        RIGHT
    </div>
</div>

CSS

html,
body,
#main-content,
#left-column,
#right-column
{
    height: 100%;
}

#left-column
{
    background-color: #ccc;
    float: left;
    width: 75%;
}

#right-column
{
    background-color: #eee;
    float: left;
    width: 25%;
}