JSFiddle - React, Tailwind, and code Playground

HTML

<div class="main-box"> 
    <div>
        <div class="top-head"><span>At top</span>
        </div>
        <div class="side"> 
            <div class="img-side"> 
                <img src="http://st2.gsmarena.com/vv/pics/htc/htc-snap-1.jpg" width="75px" height="75px" /> 
            </div> 
          <div class="post-user">User name</div>
              <div class="clearfix"></div>
          </div> 
    </div> 
</div>

CSS

.post-user { 
    background:black; 
    color:white; 
    width:auto; 
    float:left; 
    
}
.img-side {
     border-style:solid;border-width:medium;width:75px;margin-bottom:2px;
}
.top-head {
    background:cyan;
    width:100%;
    height:20px;
    display:block;
}
.main-box {
    border-style:solid;
    border-width:1px;
    display:block;
    height:auto;
}
.clearfix {
    clear:both;
}