/* Horizontal Main Nav
----------------------------------------------------------------------------------------------------*/
div#mainnav {
	position:relative;
	z-index:100;
	padding: 0px 0 0 0px;
}

div#mainnav ul {
	padding: 0px;
	margin: 0px;
	list-style-type:none;
}

div#mainnav li {
	float:left;
	position:relative;
	margin: 0px;
	padding: 0px;
	list-style-type:none;
}

/* style the links for the top level */

div#mainnav a {
	font-size: 12px;
	height: 19px;
	color: #1a1a1a;
	text-decoration: none;
	text-align:center;
	padding: 9px 12px;
	display: block;
	font-weight: bold;
	text-transform: uppercase;
	width: auto;
	margin: 0;
}

/* Style the first navigation button */
div#mainnav li:first-child a { }

div#mainnav ul li a.current { background-color:#000; }

div#mainnav a:hover,
div#mainnav ul li:hover {
	color: #FFCC00;
	background: #354356;
}

/* Drop Down CSS
----------------------------------------------------------------------------------------------------*/
div#mainnav ul ul {
	visibility:hidden;
	position:absolute;
	height: 0;
	top: 41px;
	left:0;
	z-index: 98
}

/* style the second level links */
div#mainnav ul ul a,
div#mainnav ul ul a:visited {
	background:#4c637e;
	color:#fff;
	height:auto;
	padding: 12px 5px;
	width: 200px;
	border-width:0 1px 1px 1px;
}

/* Style the first drop down navigation button */
div#mainnav ul ul li:first-child a {  }

div#mainnav ul ul a:hover,
div#mainnav:hover > a,
div#mainnav ul ul:hover > a {
	color: #FFCC00;
	background: #354356;
}

/* style the third level background */
div#mainnav ul ul ul {
	left: 211px;
	top: 0px;
	width:129px;
	position: absolute;
	z-index: 99
}

div#mainnav ul ul ul a,
div#mainnav ul ul ul a:visited {
	background:#FFCC00;
	color: #000;
}

/* Style the first drop down navigation button of a drop down */
div#mainnav ul ul ul li:first-child a {  }

div#mainnav ul ul ul a:hover {
	color: #FFCC00;
	background: #354356;
}

/* style the table so that it takes no part in the layout - required for IE to work */
div#mainnav table {
	position:absolute;
	top:0;
	left:0;
	border-collapse:collapse;
}

/* make the second level visible when hover on first level list OR link */
div#mainnav ul li:hover ul,
div#mainnav ul a:hover ul { visibility:visible; }

/* keep the third level hidden when you hover on first level list OR link */
div#mainnav ul:hover ul ul { visibility:hidden; }

/* make the third level visible when you hover over second level list OR link */
div#mainnav ul:hover ul :hover ul { visibility:visible; }

This is PURE CSS. Tested in IE7+, Chrome, Firefox, Safari and Opera

CSS Horizontal Navigation

css, navigation

CSS