CSS Problem mit ul li ul li

#l_sidebar {
	background: #F2F2F2;
	display: inline;
	float: left;
	width: 198px;
	margin: 0px 20px 0px 0px;
	padding: 0px 20px 10px 20px;
	border-left: 1px solid #D9D9D9;
	border-right: 1px solid #D9D9D9;
	border-bottom: 1px solid #D9D9D9;
	}
	
#l_sidebar p{
	padding: 5px 0px 0px 0px;
	margin: 0px;
	line-height: 17px;
	}
	
#l_sidebar h2 {
	color: #BE0C0C;
	font-size: 13px;
	font-family: verdana, arial, times new roman;
	font-weight: bold;
	margin: 20px 0px 0px 0px;
	padding: 0px 0px 5px 0px;
	border-bottom: 1px dotted #C0C0C0;
	}
	
#l_sidebar ul {
	list-style: none;
	margin: 0px;
	padding: 0px;
	}

#l_sidebar ul li {
	display: inline;
	padding: 0px;
	margin: 0px;
	}
	
#l_sidebar ul li ul li {
        background:url(images/arrow.gif) no-repeat left center;
	margin: 0px 0px 0px 0px;
	padding: 0px 0px 0px 10px;
	}
	
#l_sidebar ul li a, #l_sidebar ul li a:visited {
	display: block;
	color: #333333;
	text-decoration: none;
	padding: 5px 0px 5px 0px;
	border-bottom: 1px dotted #C0C0C0;
	}

#l_sidebar ul li a:hover {
	background: #EAEAEA;
	color: #BE0C0C;
	text-decoration: none;
	}

<li id="irgendwas">
<h2>Überschrift</h2>
<ul>
<li><a href="#">Eine Seite</a>
<ul>
<li><a href="#">Eine Unterseite</a></li>
</ul>
</li>
<li><a href="#">Weitere Seite</a></li>
<li><a href="#">Weitere Seite</a></li>
<li><a href="#">Weitere Seite</a></li>
</ul>
</li>