JSFiddle - React, Tailwind, and code Playground

HTML

<div class="content">content</div>
<div class="sideBar">sideBar</div>

CSS

*
{
 margin:0;padding:0;
}
html,body,div
{
    height: 100%;
}
.content
{
    padding-right: 500px;
    width: 100%;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
    background: yellow;
}
.sideBar
{
    position: absolute;
    top:0;
    right:0;
    width: 500px;
    background: pink;
}