<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>W3Cschool教程(w3cschool.cn)</title>
.wrapper {overflow:auto;}#main {margin-left: 4px;}#leftsidebar {float: none;width: auto;}#menulist {margin:0;padding:0;} border:1px solid #d4d4d4;
@media screen and (min-width: 480px) { #leftsidebar {width:200px;float:left;} #main {margin-left:216px;} <li class="menuitem">Menu-item 1</li>
<li class="menuitem">Menu-item 2</li>
<li class="menuitem">Menu-item 3</li>
<li class="menuitem">Menu-item 4</li>
<li class="menuitem">Menu-item 5</li>
<p>在屏幕可视窗口尺寸小于 480 像素时将菜单浮动到页面左侧。</p>