CSS - Css Drop Down Menu Flickers

#PageList1 ul {
height: 1.5em;
overflow:hidden;
margin: 10px -10px 5px;
width: 100%;
padding: 10px;
background-image:url('http://4.bp.blogspot.com/-WKkxGKrRVcw/TbFWFn_2VxI/AAAAAAAAAis/NKf1k3sO9A8/s1600/nav_bg2.jpg');
background-repeat:repeat-x;
}

#PageList1 li {
height: 1.5em;
list-style-type:none;
float:left;
}

#PageList1 li a {
display:block;
height: 1.5em;
width:auto;
clear:left;
font-weight:bold;
font-size:9pt;
line-height: 0.5em;
margin: -9px 0px -23px;
color: #ffffff;
background-image:url('http://3.bp.blogspot.com/_vhqPwC7csIg/TSUQG6Q3tfI/AAAAAAAAAYU/5ceiGi8na3s/s1600/gradient40px.jpg');
background-repeat:repeat-x;
text-align:center;
text-decoration:none;

padding: 10px 10px 15px;

	border: 1px solid #ccc;
	border-right: 0px solid #ccc;
	border-bottom: 0px solid #ccc;
	-webkit-border-radius: 5px;
	-moz-border-radius: 5px;
	border-radius: 5px;
    -moz-box-shadow: 3px 3px 4px #000;
    -webkit-box-shadow: 3px 3px 4px #000;
    box-shadow: 3px 3px 4px #000;
}
#PageList1 li a:hover, #PageList1 li a.sfhover {
background:transparent;
font-weight:bold;
color: white;
}

#PageList1 li ul {
	left: -999em;
        position: absolute;
	width: 13em; /* Width to help Opera out */
height: auto;	
background-color: #ccc; 
colour:#fff; 
clear: left;
}

#PageList1 li:hover ul, #PageList1 li.sfhover ul {
	left: auto;
	margin: 8px -80px 0px;
width: 13em;
height: auto;
background: #ccc;

}

#PageList1 li:hover li a, #PageList1 li.sfhover li a {
background:#ccc;
	border: 0px solid #ccc;
	border-right: 0px solid #ccc;
	border-bottom: 0px solid #fffccc;
	-webkit-border-radius: 0px;
	-moz-border-radius: 0px;
	border-radius: 0px;
padding: 0px;
margin: 5px 0px 0px;
    -moz-box-shadow: 0px 0px 0px #000;
    -webkit-box-shadow: 0px 0px 0px #000;
    box-shadow: 0px 0px 0px #000;
	color: #000; 
}
#PageList1 li li a:hover, #PageList1 li li a.sfhover {
	background-color: #ccc; 
color: #fff;}

<script type='text/javascript'>
sfHover = function() {
	var sfEls = document.getElementById("PageList1").getElementsByTagName("LI");
	for (var i=0; i<sfEls.length; i++) {
		sfEls[i].onmouseover=function() {
			this.className+=" sfhover";
		}
		sfEls[i].onmouseout=function() {
			this.className=this.className.replace(new RegExp(" sfhover\\b"), "");
		}
	}
}
if (window.attachEvent) window.attachEvent("onload", sfHover);
</script>

<div id="Nav">
                    <ul class="menu">
                        <li>
                            <a href="#">
                                Home
                            </a>
                        </li>
                        <li>
                            <a href="#" onclick="javascript:showlayer('sm_1')">
                                Profile
                            </a>
                            <ul class="submenu" id="sm_1">
                                <li><a href="#">Portfolio</a></li>
                                <li><a href="#">Resume</a></li>
                                <li><a href="#">About Me</a></li>
                            </ul>
                        </li>
                        <li>
                            <a href="#">
                                Contact
                            </a>
                        </li>
                        <li>
                            <a href="#" onclick="javascript:showlayer('sm_2')">
                                Login
                            </a>
                            <ul class="submenu" id="sm_2">
                                <li><a href="#">Friends</a></li>
                                <li><a href="#">Family</a></li>
                                <li><a href="#">Admin</a></li>
                            </ul>
                        </li>
                    </ul>
                </div>

ul, li
{
	margin:0; border:0; padding:0; list-style:none;
}
#Nav
{
	font-size:11px;
	color:#3b5d14;
	font-weight:bold;
	padding:4px;
	height:30px;
	font-family: Lucida Sans;
}
#Nav .menu li 
{
	/*background:url(Images/Light/Left-Menu.png) left top no-repeat;*/
	height:30px;
	float:left;
	margin-right:10px;
}
#Nav .menu li a
{
	color:#F1F1F1;
	width: 75px;
	text-decoration:none;
	padding:0 10px;
	height:30px;
	line-height:30px;
	display:block;
	float:left;
	padding:0 26px 0 10px;
	background:url(Images/Light/Right-Menu-Off.png) right top no-repeat;
	font-family: Lucida Sans;
}


#Nav .menu li a:hover
{
	color:#666666;
	background: url(Images/Light/MenuRight.png) right top no-repeat;
}

#Nav .menu li:hover
{
		
	background: url(Images/Light/Menu-Hover.png) left top no-repeat;
}

#Nav ul .submenu 
{
	border:solid 1px #7ea3bb;
	margin-left: auto;
	margin-right: auto;
	/*border-top:none;*/
	background:#FFFFFF;
	position:relative;
	top:1px;
	width:100px;
	padding:6px 0;
	clear:both;
	z-index:2;
	display:none;
	filter:progid:DXImageTransform.Microsoft.Alpha(opacity=90);opacity:.95
}
#Nav ul .submenu li
{
	background:none;
	display:block;
	float:none;
	margin:0 6px;
	border:0;
	height:auto;
	line-height:normal;
	/*border-top:solid 1px #DEDEDE;*/
}
#Nav .submenu li a
{
	background:none;
	display:block;
	float:none;
	padding:6px 6px;
	margin:0;
	border:0;
	height:auto;
	color:#105cbe;
	line-height:normal;
}
#Nav .submenu li a:hover
{
	background:#ebf4fa;
}