JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="main-nav">
    <li><a href="#">one</a></li>
    <li><a href="#">two</a></li>
    <li><a href="#">three</a></li>
</ul>

<hr />

<ul id="main-nav">
    <li><a href="#">one</a></li>
    <li><a href="#">two</a></li>
    <li><a href="#">three</a></li>
    <li><a href="#">four</a></li>
    <li><a href="#">five</a></li>
</ul>

CSS

#main-nav {
    list-style: none;
    margin: 0;
    padding: 0;
    width: 100%;
    display: table;
    table-layout: fixed;
    overflow: hidden
}
#main-nav li {
    display: table-cell;
    *float: left; /* improve IE7 */
    height: 25px;
    text-align: center;
    padding-left: 5px
}
#main-nav li:first-child {
    padding-left: 0
}
#main-nav li a {
    width: 100%;
    display: block;
    height: 100%;
    line-height: 25px;
    text-decoration: none;
    background-color: #e0e0f0;
    font-weight: bold;
    color: #021020;
}
#main-nav li a:hover {
    background-color: #498cd5;
    color: #ddeeee;
}