/* We need the extra javascript code 

<script language="JavaScript" type="text/JavaScript">

navHover = function() {
	var lis = document.getElementById("navmenu-h").getElementsByTagName("LI");
	for (var i=0; i<lis.length; i++) {
		lis[i].onmouseover=function() {
			this.className+=" iehover";
		}
		lis[i].onmouseout=function() {
			this.className=this.className.replace(new RegExp(" iehover\\b"), "");
		}
	}
}
if (window.attachEvent) window.attachEvent("onload", navHover);

</script>

And HTML code

  <ul id="navmenu-h">
    <li><a href="#">Opt1</a></li>
    <li><a href="#">Opt2 >></a>
      <ul>
        <li><a href="#">Opt2.1 >></a>
          <ul>
            <li><a href="#">Opt2.1.1</a></li>

            <li><a href="#">Opt2.1.2</a></li>
            <li><a href="#">Opt2.1.3</a></li>
            <li><a href="#">Opt2.1.4</a></li>
          </ul>
        </li>
        <li><a href="#">Opt2.2</a></li>
        <li><a href="#">Opt2.1.2</a></li>
      </ul>
    </li>
  </ul>
*/

ul#navmenu-h {
	font: 80% "Trebuchet MS", Arial, Helvetica, sans-serif;
 	margin: 0;
	border: 0 none;
	padding: 0;
	width: 700px; /*For KHTML*/
	list-style: none;
	height: 32px;
	margin-left: 30px;
}

ul#navmenu-h li {
  margin: 0;
  border: 0 none;
  padding: 0;
  float: left; /*For Gecko*/
  display: inline;
  list-style: none;
  position: relative;
  height: 31px;
}

ul#navmenu-h ul {
  margin: 0;
  border: 0 none;
  padding: 0;
  width: 190px;
  list-style: none;
  display: none;
  position: absolute;
  top: 31px;
  left: 0;
}

ul#navmenu-h ul:after /*From IE 7 lack of compliance*/{
  clear: both;
  display: block;
  font: 1px/0px serif;
  content: ".";
  height: 0;
  visibility: hidden;
}

ul#navmenu-h ul li {
  width: 190px;
  float: left; /*For IE 7 lack of compliance*/
  display: block !important;
  display: inline; /*For IE*/
}

/* Root Menu */
ul#navmenu-h a {
	text-decoration: none;
	color: #cccccc;
	background: url(../../images/design/menu/celda.gif) repeat-x top left; 
	display: block;
	padding: 9px 12px;
	text-align: left;
	float: none !important; /*For Opera*/
	float: left; /*For IE*/
	display: block;
	text-decoration: none;
	height: auto !important;
	height: 1%; /*For IE*/
}

/* Root Menu Hover Persistence */
ul#navmenu-h a:hover,
ul#navmenu-h li:hover a,
ul#navmenu-h li.iehover a {
	color: #363636;
	background: url(../../images/design/menu/celdaL.gif) repeat-x top left; 
  
}

/* 2nd Menu */
ul#navmenu-h li:hover li a,
ul#navmenu-h li.iehover li a {
	float: none;
	color: #cccccc;
	background: url(../../images/design/menu/celdaSub1.gif) repeat-x top left; 
}

/* 2nd Menu Hover Persistence */
ul#navmenu-h li:hover li a:hover,
ul#navmenu-h li:hover li:hover a,
ul#navmenu-h li.iehover li a:hover,
ul#navmenu-h li.iehover li.iehover a {
	float: none;
	color: #363636;
	background: url(../../images/design/menu/celdaSub2.gif) repeat-x top left; 
}

/* 3rd Menu */
ul#navmenu-h li:hover li:hover li a,
ul#navmenu-h li.iehover li.iehover li a {
	color: #cccccc;
	background: url(../../images/design/menu/celdaSub1.gif) repeat-x top left; 
}

/* 3rd Menu Hover Persistence */
ul#navmenu-h li:hover li:hover li a:hover,
ul#navmenu-h li:hover li:hover li:hover a,
ul#navmenu-h li.iehover li.iehover li a:hover,
ul#navmenu-h li.iehover li.iehover li.iehover a {
	color: #363636;
	background: url(../../images/design/menu/celdaSub2.gif) repeat-x top left; 
}

/* 4th Menu */
ul#navmenu-h li:hover li:hover li:hover li a,
ul#navmenu-h li.iehover li.iehover li.iehover li a {
	color: #cccccc;
	background: url(../../images/design/menu/celdaSub1.gif) repeat-x top left; 
}

/* 4th Menu Hover */
ul#navmenu-h li:hover li:hover li:hover li a:hover,
ul#navmenu-h li.iehover li.iehover li.iehover li a:hover {
  background: #CCC;
  color: #FFF;
}

ul#navmenu-h ul ul,
ul#navmenu-h ul ul ul {
  display: none;
  position: absolute;
  top: 0;
  left: 190px;
}

/* Do Not Move - Must Come Before display:block for Gecko */
ul#navmenu-h li:hover ul ul,
ul#navmenu-h li:hover ul ul ul,
ul#navmenu-h li.iehover ul ul,
ul#navmenu-h li.iehover ul ul ul {
  display: none;
}

ul#navmenu-h li:hover ul,
ul#navmenu-h ul li:hover ul,
ul#navmenu-h ul ul li:hover ul,
ul#navmenu-h li.iehover ul,
ul#navmenu-h ul li.iehover ul,
ul#navmenu-h ul ul li.iehover ul {
  display: block;
}



/* SIMPLE MENU */
ul#simplemenu-h {
	font: 90% "Trebuchet MS", Arial, Helvetica, sans-serif;
 	margin: 0;
	border: 0 none;
	padding: 0;
	width: 700px; /*For KHTML*/
	list-style: none;
	height: 28px;
	margin-left: 10px;
    z-index:5;
}

ul#simplemenu-h li {
  margin: 0;
  border: 0 none;
  padding: 0;
  float: left; /*For Gecko*/
  display: inline;
  list-style: none;
  position: relative;
  height: 27px;
    z-index:5;
}

ul#simplemenu-h ul {
  margin: 0;
  border: 0 none;
  padding: 0;
  width: 190px;
  list-style: none;
  display: none;
  position: absolute;
  top: 28px;
  left: 0;
  padding-top:1px;  
    z-index:5;
}

ul#simplemenu-h ul:after /*From IE 7 lack of compliance*/{
  clear: both;
  display: block;
  font: 1px/0px serif;
  content: ".";
  height: 0;
  visibility: hidden;
    z-index:5;
}

ul#simplemenu-h ul li {
  width: 170px;
  float: left; /*For IE 7 lack of compliance*/
  display: block !important;
  display: inline; /*For IE*/
  background-color: #1d4362; 
  border-top: 1px solid #ddd;
    z-index:5;
}

/* Root Menu */
ul#simplemenu-h a {
	text-decoration: none;
	color: #fff;
	display: block;
	padding: 6px 12px;
	text-align: left;
	float: none !important; /*For Opera*/
	float: left; /*For IE*/
	display: block;
	text-decoration: none;
	height: auto !important;
	height: 1%; /*For IE*/
    z-index:5;
}

/* Root Menu Hover Persistence */
ul#simplemenu-h a:hover,
ul#simplemenu-h li:hover a,
ul#simplemenu-h li.iehover a {
	color: yellow; 
    z-index:5;
}

/* 2nd Menu */
ul#simplemenu-h li:hover li a,
ul#simplemenu-h li.iehover li a {
	float: none;
	color: #white;
    z-index:5;
}


/* 2nd Menu Hover Persistence */
ul#simplemenu-h li:hover li a:hover,
ul#simplemenu-h li:hover li:hover a,
ul#simplemenu-h li.iehover li a:hover,
ul#simplemenu-h li.iehover li.iehover a {
	float: none;
	color: yellow;
    z-index:5;
}

ul#simplemenu-h ul ul,
ul#simplemenu-h ul ul ul {
  display: none;
  position: absolute;
  top: 0;
  left: 190px;
    z-index:5;
}

/* Do Not Move - Must Come Before display:block for Gecko */
ul#simplemenu-h li:hover ul ul,
ul#simplemenu-h li:hover ul ul ul,
ul#simplemenu-h li.iehover ul ul,
ul#simplemenu-h li.iehover ul ul ul {
  display: none;
    z-index:5;
}

ul#simplemenu-h li:hover ul,
ul#simplemenu-h ul li:hover ul,
ul#simplemenu-h ul ul li:hover ul,
ul#simplemenu-h li.iehover ul,
ul#simplemenu-h ul li.iehover ul,
ul#simplemenu-h ul ul li.iehover ul {
  display: block;
    z-index:5;
}