JSFiddle - React, Tailwind, and code Playground

HTML

<div id="content">

</div>
<div id="button-wrap">
    <div id="backToTop">
        <a href="#t">img</a>
    </div>
</div>

CSS

#button-wrap {
  position: fixed;
  bottom: 0px;
  left: 0px;
  width:100%;
}
#backToTop {
  position:relative;
  width:500px;
  margin:0 auto;
  z-index: 1000;
  color: #C6C6C6;
  opacity: 0.3;
}
#content {
  position:relative;
  width:500px;
  height:10000px;
  margin:0 auto;
  background-color:#888;
}
a {
  height:50px;
  width:50px;
  background-color:#cc0000;   
}