JSFiddle - React, Tailwind, and code Playground

HTML

<div id="wrapper">
    <div id="content">
         <!-- A element with more width than 100% -->
        <div style="width:110%;border-right:10px solid black;height:200px;background:yellow;"></div>
    </div>
    <div id="left-panel"></div>
</div>

CSS

*{
 margin:0;
 padding:0;
}
#wrapper{
    position:fixed;
    top:0;
    left:0;
    background:gray;
    width:100%;
    height:100%;
    overflow:auto;
}
#left-panel{
    position:fixed;
    top:0;
    left:0;
	width:200px;
    height:100%;
    background:red;
}