JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
        <li>first item</li>
        <li>second item</li>
        <li>third item</li>
    </ul>
    <div class="c1">ZZZ</div>

CSS

ul {
            border: 1px solid red;            
            margin:0 0 0px 0;
            
        }
        .c1 {
            border: 1px solid green;
            height:50px;
            width:100%;
        }