JSFiddle - React, Tailwind, and code Playground

HTML

<body>
<div class="div1">
</div>

<div class="div2">
</div>

<div class="div3">sss
</div>

</body>

CSS

body {margin:0;padding:0;background-color:#cecece;min-height:1000px;}

.div1 {
  width:100%;
  height:70px;
	position: fixed;
  z-index:1;
  background-color: #fff;
}

.div2 {
  width:100%;
  height:70px;
	position: fixed;
  z-index:1;
  top: 70px;
  background-color: #000;
}

.div3 {
}