JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="menu">
	
	<li>
		<a href="#">Categories</a>
		<ul>
			<li>
				<a href="#">CSS</a>
				<ul>
					<li><a href="#">Item 11</a></li>
					<li><a href="#">Item 12</a></li>
					<li><a href="#">Item 13</a></li>
					<li><a href="#">Item 14</a></li>
				</ul>				
			</li>
			<li>
				<a href="#">Graphic design</a>
				<ul>
					<li><a href="#">Item 21</a></li>
					<li><a href="#">Item 22</a></li>
					<li><a href="#">Item 23</a></li>
					<li><a href="#">Item 24</a></li>
				</ul>				
			</li>
			<li>
				<a href="#">Development tools</a>
				<ul>
					<li><a href="#">Item 31</a></li>
					<li><a href="#">Item 32</a></li>
					<li><a href="#">Item 33</a></li>
					<li><a href="#">Item 34</a></li>
				</ul>				
			</li>
			<li>
				<a href="#">Web design</a>				
				<ul>
					<li><a href="#">Item 41</a></li>
					<li><a href="#">Item 42</a></li>
					<li><a href="#">Item 43</a></li>
					<li><a href="#">Item 44</a></li>
				</ul>	
			</li>
		</ul>
	</li>
  </ul>

CSS

body
{
    width: 960px;
    margin: 40px auto;
}

/* Main menu */

#menu
{
    width: 100%;
    margin: 0;
    padding: 10px 0 0 0;
    list-style: none;
    background: #111;
    background: -moz-linear-gradient(#444, #111);
    background: -webkit-gradient(linear,left bottom,left top,color-stop(0, #111),color-stop(1, #444));
    background: -webkit-linear-gradient(#444, #111);
    background: -o-linear-gradient(#444, #111);
    background: -ms-linear-gradient(#444, #111);
    background: linear-gradient(#444, #111);
    -moz-border-radius: 50px;
    border-radius: 50px;
    -moz-box-shadow: 0 2px 1px #9c9c9c;
    -webkit-box-shadow: 0 2px 1px #9c9c9c;
    box-shadow: 0 2px 1px #9c9c9c;
}

#menu li
{
    float: left;
    padding: 0 0 10px 0;
    position: relative;
    line-height: 0;
}

#menu a
{
    float: left;
    height: 25px;
    padding: 0 25px;
    color: #999;
    text-transform: uppercase;
    font: bold 12px/25px Arial, Helvetica;
    text-decoration: none;
    text-shadow: 0 1px 0 #000;
}

#menu li:hover > a
{
    color: #fafafa;
}

*html #menu li a:hover /* IE6 */
{
    color: #fafafa;
}

#menu li:hover > ul
{
    display: block;
}

/* Sub-menu */

#menu ul
{
    list-style: none;
    margin: 0;
    padding: 0;
    display: none;
    position: absolute;
    top: 35px;
    left: 0;
    z-index: 99999;
    background: #444;
    background: -moz-linear-gradient(#444, #111);
    background: -webkit-gradient(linear,left bottom,left top,color-stop(0, #111),color-stop(1, #444));
    background: -webkit-linear-gradient(#444, #111);
    background: -o-linear-gradient(#444, #111);
    background: -ms-linear-gradient(#444, #111);
    background: linear-gradient(#444, #111);
    -moz-box-shadow: 0 0 2px rgba(255,255,255,.5);
    -webkit-box-shadow: 0 0 2px rgba(255,255,255,.5);
    box-shadow: 0 0 2px rgba(255,255,255,.5);
    -moz-border-radius: 5px;
    border-radius: 5px;
}

#menu ul ul
{
    top: 0;
    left: 150px;
}

#menu ul li
{
    float: none;
   ...

JavaScript

$(function() {
        if ($.browser.msie && $.browser.version.substr(0,1)<7)
        {
            $('li').has('ul').mouseover(function(){
                $(this).children('ul').show();
            }).mouseout(function(){
                $(this).children('ul').hide();
            })
        }
    });