Css 下拉位置

在获取下拉菜单位置或主要是下拉菜单链接的背景时遇到一些问题，无法找出问题所在。。。下面是CSS代码（菜单li ul）的图像，显示了它的外观->或JSFIDLE

基本消除 .menu li{左：50%} 加 .menu li a{left:0；}

现在是这样，中心效果消失了（也许我应该提到我想要菜单中心）

.menu ul{
background-color: transparent;
height: 25px;
list-style: none;
margin: 0;
padding: 0;
position: relative;
clear: left;
float: right;
text-align: center;
right: 50%;

}
.menu li{
    float: left;
    padding: 0px;
    position: relative;
    left: 50%;
    margin: 0px;
    list-style: none;
    }

.menu li a{ /* Where main link names are etc */
    background: #333 url("images/seperator.gif") bottom right no-repeat;
    color: #CCC;
    display: block;
    font-weight: normal;
    line-height: 35px;
    margin: 0px;
    padding: 0px 25px;
    text-align: center;
    text-decoration: none;
    }

    .menu li a:hover, .menu ul li:hover a{
        background-color: #2580A2;
        background-image: url('images/hover.gif');
        background-position: bottom center;
        background-repeat: no-repeat;
        color:#FFFFFF;
        text-decoration:none;
        }

.menu li ul{ /* Drop down menu */
    background-color: #333;
    display: none;
    height: auto;
    border: 0px;
    position: absolute;
    width: 225px;
    z-index: 200;
    padding: 0px;
    margin: 0px;
    border: 0px;
    }

.menu li:hover ul{
    display: block;
    }

.menu li li {
    background: url('images/sub_sep.gif') bottom left no-repeat;
    display: block;
    float: none;
    width: 220px;
    }

.menu li:hover li a{
    background: none;

    }

.menu li ul a{
    display: block;
    height: 35px;
    font-size: 12px;
    font-style: normal;
    margin: 0px;
    padding: 0px 10px 0px 15px;
    text-align: left;
    }

    .menu li ul a:hover, .menu li ul li:hover a{
        background: #2580A2;
        background-image: url(images/hover_sub.gif);
        background-position: center left;
        background-repeat: no-repeat;
        border: 0px;
        color: #FFF;
        text-decoration: none;
        }

.menu p{
    clear: left;
    }