代码
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
nav{
margin: 5px
width: 100pxheight: 200px
background-color: red
float: right
}
</style>
</head>
<body>
<nav class="right">右</nav>
<nav>中</nav>
<nav>左</nav>
</body>
</html>
<div id="a" style="width:100%"><div id="b" style="width:980pxmargin:0 auto">
<span id="3" style="float:right">z</span><span id="1">x</span><span id="2">y</span>
</div>
</div>这样子吗??