JSFiddle - React, Tailwind, and code Playground

HTML

<div class="main">
<div id="header"><p>Header</p></div>
</div>

CSS

.main{
    width:100%;
    height:2000px;
}

#header{
    width:100%;
    height:100px;
    position:fixed;
    top:0;left:0;
    background:yellow;
}