无论用户使用什么分辨率,我如何确保导航栏只占用一行(缩小到适合)？

这是导航栏的CSS代码.请注意,在导航下我已将宽度设置为33.3％并填充相同以使按钮居中.我不知道这是不是原因.

nav {
    display:block;
    position: absolute;
    left:0; 
    white-space:nowrap; 
    margin: 0 auto; 
    width: 33.3%; 
    background-color:#ff6600;
    padding-left: 33.3%; 
    padding-right: 33.3%; 
} 
 
nav ul { 
    margin: 0 auto; 
    width: 100%; 
    list-style: none;
    display: inline;
    white-space:nowrap; 
} 
 
nav ul li { 
    float: left;
    position: relative;
    white-space:nowrap; 
} 
 
nav ul li a { 
    display: block; 
    margin: 0 auto; 
    width: 150px; 
    font-size: 16px;
    font-family: century gothic; 
    line-height: 44px; 
    text-align: center; 
    text-decoration: none; 
    color:#575757;
    white-space:nowrap; 
} 
 
nav ul ul { 
    width: 200px;
    position:absolute; 
    top:-99999px; 
    left:0; 
    opacity: 0; 
    -webkit-transition: opacity .4s ease-in-out; 
    -moz-transition: opacity .4s ease-in-out; 
    -o-transition: opacity .4s ease-in-out; 
    transition: opacity .4s ease-in-out; 
    z-index:497; 
    background:#333; 
    padding: 2px; 
    border:1px solid #444; 
    border-top:none; 
    Box-shadow:#111 0 3px 4px; 
}
 
 
nav ul ul li a { 
    display: block;
    width: 200px;
    text-align: left;
    padding-left: 3px;
    font-size: 14px;    
}   
 
 
 
nav ul li:hover>ul{
    opacity: 1; 
    position:absolute; 
    top:98%; 
    left:0;
 
}
 
 
nav ul li a:hover { 
    color: #fff;
    background-color: #cc3300 
} 
 
nav ul li.selected a { 
    color: #fff; 
    background-color: #cc3300; 
}