JSFiddle - React, Tailwind, and code Playground

HTML

<div id='container'>
    <div id='left'>&nbsp;</div><div id='right'>&nbsp;</div>
</div>

<div id='spacer' style='height: 50px;'></div>

<div id="float_container">
    <div id="float_left">&nbsp;</div>
    <div id="float_right">&nbsp;</div>
    <div class="float_clear"></div>
</div>

CSS

/* regular flow */
#container {
    width: 300px;
    margin: 0px;
    padding: 0px;
    border: 0px;
}

#left {
    margin: 0px;
    padding: 0px;
    border: 0px;
    background: orange;
    width: 150px;
    display: inline-block;
}

#right {
    margin: 0px;
    padding: 0px;
    border: 0px;
    background: green;
    width: 150px;
    display: inline-block;
}

/* foat flow */
#float_container {
    width: 300px;
}

#float_left {
    float: left;
    width: 150px;
    background: orange;
}

#float_right {
    float: right;
    width: 150px;
    background: green;
}

#float_clear {
    clear: both;
}