ドロップダウン メニューが出てきません_html/css_WEB-ITnose

<div class="navbar">		<ul>			<li><a href="#" id="a1">首页</a></li>			<li><a href="#" id="a2">车站简介</a></li>			<li><a href="#" id="a3">班线简介</a>				<ul> 					<li class="opacity submenu_bottom"><a href="bcxl.jsp">主营班线</a></li>					<li class="opacity submenu_bottom"><a href="bccx.jsp">班次查询</a></li>				</ul>			</li>

/*导航条*/.navbar{ width:1000px;height:38px; background:url(../images/navbar.jpg) no-repeat; margin:0 auto;}.navbar ul li{ height:38px; line-height:38px; float:left; text-align:center; width:100px;}.navbar ul li a{height:38px; line-height:32px; font-size:15px; font-weight:bold; text-decoration:none; display:block; font-family: "微软雅黑"; color:#000000; }.navbar ul li a.click,.navbar ul li a:hover{color:#FFFFFF; background:url(../images/navbar_a.png)  no-repeat;}.navbar ul li a div{ background:#f00; display:none;}.navbar li ul li{ float: left;width: 100px;}.navbar li ul li.submenu_bottom{ float: left; width: 100px; background: url(../images/navbar_a.png) no-repeat; height:32px; font-weight:normal; }.navbar li ul li a{ display: block; width: 100px;text-align:center;text-decoration:none; background:none; } .navbar li ul li a:hover { color:#fff; text-decoration:none;font-weight:normal; /*background:#B97136;*/ background:#10BAF0; } .navbar li ul li.submenu_bottom a:hover{ float: left; width: 100px; background: url(../images/navbar_a.png) left -31px no-repeat; height:32px; font-weight:normal; }  .navbar li:hover ul { left: auto;}