一个div宽度不固定的左右居中效果

html,body,div,span,applet,object,iframe,h1,h2,h3,h4,h5,h6,p,blockquote,pre,a,abbr,acronym,address,big,cite,code,del,dfn,em,font,img,ins,kbd,q,s,samp,small,strike,strong,sub,sup,tt,var,dl,dt,dd,ol,ul,li,fieldset,form,label,legend,table,caption,tbody,tfoot,thead,tr,th,td {
border:0;
outline:0;
margin:0;
padding:0;
}

.PageNav{
float:left;
width:100%;
padding:20px 0px;
}

.pagination {
height: 36px;
margin: 18px 0;
}
.pagination ul {
display: inline-block;
*display: inline;
/* IE7 inline-block hack */
*zoom: 1;
margin-left: 0;
margin-bottom: 0;
-webkit-border-radius: 3px;
-moz-border-radius: 3px;
border-radius: 3px;
-webkit-box-shadow: 0 1px 2px rgba(0, 0, 0, 0.05);
-moz-box-shadow: 0 1px 2px rgba(0, 0, 0, 0.05);
box-shadow: 0 1px 2px rgba(0, 0, 0, 0.05);
background:#f8f8f8;
}
.pagination li {
display: inline;
}
.pagination a {
float: left;
padding: 0 14px;
line-height: 34px;
text-decoration: none;
border: 1px solid #ddd;
border-left-width: 0;
color:#666;
font-size:14px;
font-family:"黑体";
}
.pagination a:hover,
.pagination .active a {
background-color: #efefef;
}
.pagination .active a {
color: #004ea2;
cursor: default;
}
.pagination .disabled span,
.pagination .disabled a,
.pagination a:hover,
.pagination .disabled a:hover {
color: #004ea2;
background-color: transparent;
cursor: default;
}
.pagination li:first-child a {
border-left-width: 1px;
-webkit-border-radius: 3px 0 0 3px;
-moz-border-radius: 3px 0 0 3px;
border-radius: 3px 0 0 3px;
}
.pagination li:last-child a {
-webkit-border-radius: 0 3px 3px 0;
-moz-border-radius: 0 3px 3px 0;
border-radius: 0 3px 3px 0;
}
.pagination-centered {
text-align: center;
}

html:

<div class="PageNav">
<div class="pagination pagination-centered">
<ul>
<li><a href="#">上一页</a></li>
<li class="active">
<a href="#">1</a>
</li>
<li><a href="#">2</a></li>
<li><a href="#">3</a></li>
<li><a href="#">...</a></li>
<li><a href="#">7</a></li>
<li><a href="#">下一页</a></li>
</ul>
</div>
</div>