JSFiddle - React, Tailwind, and code Playground

HTML

<div class="mobile_main">
    <div class="header">
        header
    </div>
    <div class="body_main">
        
    </div>
      <div class="footer_mobile">
          footer
      </div>
</div>

CSS

.mobile_main{
    position:relative;
}
.body_main{
    background:grey;
    min-height:300px;
 
}
.footer_mobile{
    width:100%;
    position:absolute;
    bottom:0px;
    left:0px;
    background:lightblue;
    
}
.header{
    background:yellow;
}