JSFiddle - React, Tailwind, and code Playground

HTML

<div id="maincontainer">
    <div id="contentwrapper">
        <div id="left">
            left
        </div>
    </div>
    <div id="right">
        right
    </div>
</div>

CSS

#contentwrapper {
    float: left;
    width: 100%;
}

#left {
    background-color:#FF0000;
}

#right {
    float: left;
    width: 150px; /*Width of right column in pixels*/
    margin-left: -150px; /*Set left margin to -(RightColumnWidth) */
    background-color:#00FF00;
}