JSFiddle - React, Tailwind, and code Playground

HTML

<div id="leftblock">id="leftblock"</div>
<div id="rightBlock">id="rightBlock"</div>

CSS

#leftblock {
    margin-left: 20%;
    background-color: red;
    float: left;
    height: 100px;
    width: 3px;
}
#rightBlock {
    margin-right: 20%;
    background-color: red;
    float: right;
    height: 100px;
    width: 3px;
}