JSFiddle - React, Tailwind, and code Playground

HTML

<div id="header">
    Header
</div>
<div id="leftcol">
    FOO<br /><br />
    BAR<br /><br />
    FOO<br /><br />
    BAR<br /><br />
    FOO<br /><br />
    BAR<br /><br />
    FOO<br /><br />
    BAR<br /><br />
    FOO<br /><br />
    BAR<br /><br />
    FOO<br /><br />
    BAR<br /><br />
    FOO<br /><br />
    BAR<br /><br />
    FOO<br /><br />
    BAR<br /><br />    
</div>
<div id="rightcol">
    Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br />Stuff stuff stuff<br...

CSS

#leftcol {
    
    display: inline; 
    position:fixed;
    width:100px;
    background-color: red;
}

#rightcol {
    margin-left: 120px;
    background-color: #ddd;
}