JSFiddle - React, Tailwind, and code Playground

HTML

<div id="mainContent">
<a href="http://aaa.com"><img id="theme" src="https://ssl.gstatic.com/ui/v1/icons/mail/logo_default.png" /></a>
<a class="other" href="http://xyz.com">testlink</a>
</div>

CSS

#mainContent {
    position:relative;
    height:200px;
    width:400px;
}
#theme {
  position:absolute; 
  width:100%;
  height:100%;
  top:0;
  left: 0;
  z-index: 0;
}
.other {
    position:relative;
    z-index: 2;
    background-color:#ddf;
}