JSFiddle - React, Tailwind, and code Playground

HTML

<div id='container'>
<ul id="menu">
<li><a href="#">HOME</a></li>
<li><a href="#">TREATMENTS</a>
    <ul>
        <li><a href="#">Claim Kandi</a></li>
        <li><a href="#">Claim Kandi2</a></li>
        <li><a href="#">Claim Kandi3</a></li>
    </ul>
</li>
<li><a href="#">ABOUT</a></li>
<li><a href="#">GALLERY</a></li>
<li><a href="#">CONTACT</a></li>
<li><a href="#">BOOKING</a></li>
</ul>

</div>

CSS

body{
    margin:0;
    padding:0;
}
#container{
    height:3000px;
}

#menu {
min-width: 100%;
list-style:none;
border-top: 1px solid #ccc;
border-left: 1px solid #ccc;
border-bottom: 1px solid #ccc;
position: fixed;
top:0;
background-color:#666;
text-align: center;
}