html5 중 ulli 가운데 정렬

@charset "utf-8";/* CSS Document */
/*        */
body{margin:0px;    padding:0px;}
header{
    margin:0px;
    padding:0px;
    background-color:#222222;
    color:#FFF;
    height:200px;
}
header ul{
    list-style-type:none;
    position:relative;
     left:43%;
     float:left;
}
header ul li{
    font-size:16px;
    position:relative;
    right:50%;
    float:left;
    margin-left:50px;
}