JSFiddle - React, Tailwind, and code Playground

HTML

<body>
  <div class="body">
      <div class="content">test</div>
      <div class="SideBarFirst">
          <div>not working for center</div>
      </div>
    </div>
</body>

CSS

body {
    width: 960px;
    margin: 0 auto;
} 

.content {width:500px; float : left;}

.SideBarFirst {width:460px; float : right;}

.SideBarFirst div {
    width: 40px;
    margin: 0 auto; 
}