关于网站下拉导航的设置

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<div class="head">
        <div class="logo"></div>
        <div  id="navigation">     
          <ul>
            <li class="mr70px"><a href="#" id="current">HOME</a></li>
            <li class="mr70px"><a href="#">ABOUT US</a>
              <ul>
                <li><a href="#">Careers</a></li>
              </ul>
            </li>
            <li class="mr70px"><a href="#">PRACTICE AREAS</a>
              <ul >
                <li><a href="#">State Income & Franchise Tax</a></li>
                <li><a href="#">Sales & Use Tax</a></li>
                <li><a href="#">Other Indirect Taxes</a></li>
              </ul>
            </li>
            <li class="mr70px"><a href="#">NEWS & EVENTS</a></li>
            <li><a href="#">CONTACT US</a></li>
          </ul>
        </div>
        <div class="clear"></div>
      </div>
-----------------------

ul li {
    list-style:none;
}

#navigation {
    float:right;
    /*width:715px;*/
    margin-top:0px;
}
#navigation ul li {
    float:left;
    font-size:14px;
    font-weight:bold;
    color:#666666;
}
#navigation ul li a {
    color:#086574;
    display:block;
}
#navigation ul li a:hover, #navigation ul li a#current {
    color:#944243;
}
#navigation li ul {
        /*核心内容*/
    line-height: 27px;
    text-align:left;
    left:999em;
    width:210px;
    position: absolute;
    z-index:2;
}
#navigation li ul li {
    width:210px;
    background:#fff;
}
#navigation li ul a {
    display: block;
    width:200px;
    text-align:left;
    padding-left:10px;
    font-size:12px;
        background: none;
}
#navigation li ul a:hover {
    color:#F3F3F3;
    background:#04505D;

}
#navigation li:hover ul {
    left: auto;
}