CSS:
        .menu
        {
            list-style-type:none;
        }
        .menu li
        {
            float:left;
            background:blue;
            padding:20px;
        }
        .menu li a:hover
        {
            text-decoration:underline;
        }
        .menu li a
        {
            color:#fff;
            text-decoration:none;
        }
       
        /* more menu */
        li.moreitem > a
        {
            background:blue url(more-icon.gif) right center no-repeat;
            padding-right:25px;
        }
        li.moreitem
        {
            position:relative;             
        }
        .moredropdown div
        {
            padding:5px 0;
        }
        .moredropdown
        {
            display:none;
            position: absolute;
            background:blue;
            padding:5px;
            margin-top:20px;
            top:35px;
            left:0;
            width:180px;
        }
        li.moreitem:hover .moredropdown
        {
            display:block;
        }
   
HTML:
  <ul class="menu">
    <li><a href="http://giancon.me">Trang chủ</a></li>
    <li><a href="http://giancon.me/css">CSS</a></li>
    <li><a href="http://giancon.me/qa">hỏi đáp</a></li>
    <li class="moreitem">
        <a href="http://giancon.me/css">More</a>
        <div class="moredropdown">
            <div><a href="http://sieuthidiaocsaigon.com">Siêu thị địa ốc Sài Gòn</a></div>
            <div><a href="http://nhocconan.com">Đọc truyện online</a></div>
            <div><a href="http://www.modules2buy.com">Mạng xã hội</a></div>
            <div><a href="http://www.codethietkeweb.com">Share code</a></div>
        </div>
    </li>
  </ul>