JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<body>
    <div id="window">
        <nav id="nav_wrap">
            <div id="navigation">
                <ul class="top-level">
                    <li><a href="#">Home</a>

                        <ul class="sub-level">
                            <li><a href="#">Sub Menu Item 1</a>
                            </li>
                            <li><a href="#">Sub Menu Item 2</a>
                            </li>
                            <li><a href="#">Sub Menu Item 3</a>
                            </li>
                            <li><a href="#">Sub Menu Item 3</a>
                            </li>
                        </ul>
                    </li>
                    <li><a href="#">About</a>
                    </li>
                    <li><a href="#">Contact</a>
                    </li>
                    <li> <a href="#">FAQ</a>

                        <ul class="sub-level">
                            <li><a href="#">Sub Menu Item 1</a>
                            </li>
                            <li><a href="#">Sub Menu Item 3</a>
                            </li>
                        </ul>
                    </li>
                    <li> <a href="#">News</a>

                        <ul class="sub-level">
                            <li><a href="#">Sub Menu Item 1</a>
                            </li>
                            <li><a href="#">Sub Menu Item 2</a>
                            </li>
                            <li><a href="#">Sub Menu Item 3</a>
                            </li>
                        </ul>
                    </li>
                </ul>
            </div>
        </nav>
    </div>
</body>

CSS

html, body {
    background:#78C2A9;
    margin: 0 0 0 0;
}
#window {
    height:630px;
    width: 1200px;
    margin: 20px auto 0 auto;
    padding: 0;
    background: orange;
}
#nav_wrap {
    width: 150px;
    height: 630px;
    /* Spans the height of the page */
    margin: 0;
    /* Ensures there is no space between sides of the screen and the menu */
    /* z-index: 99;  Makes sure that your menu remains on top of other page elements */
    background-color: #E95644;
}
#navigation {
    font-size:0.75em;
    width:150px;
}
#navigation ul {
    margin:0px;
    padding:0px;
}
#navigation li {
    list-style: none;
}
ul.top-level {
    background:#666;
}
ul.top-level li {
    border-bottom: #fff solid;
    border-top: #fff solid;
    border-width: 1px;
}
#navigation a {
    color: #fff;
    cursor: pointer;
    display:block;
    height:25px;
    line-height: 25px;
    text-indent: 10px;
    text-decoration:none;
    width:100%;
}
#navigation a:hover {
    text-decoration:underline;
}
#navigation li:hover {
    background: #f90;
    position: relative;
}
ul.sub-level {
    display: none;
}
li:hover .sub-level {
    background: #999;
    border: #fff solid;
    border-width: 1px;
    display: block;
}