用绝对定位
position:absolute;
top，bottom，left，right指定固定位置
<!DOCTYPE html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
</head>
<body>
<style>
.demo1{
width:300px;
height:200px;
display:block;
background:pink;
position:absolute;
top:20px;
left:50px;
}
.demo2{
width:300px;
height:200px;
display:block;
background:blue;
position:absolute;
top:400px;
right:140px;
}
</style>
<ul>
<li class="demo1">demo1</li>
<li class="demo2">demo2</li>
</ul>
</body>
</html>