织梦栏目菜单多于10个怎么修改

.header .nav{
 width:100%;
 height:64px;
 background:url(../images/nav-bg.gif) repeat-x;
 clear:both;
 overflow:hidden;
}
.header .nav ul{
 height:64px;
 margin:0px auto;
 overflow:hidden;
}