<html>
<head>
<title>Div example</title>
</head>
<body>
<style type="text/css">
.left {
float: left;
width: 120px;
height: 40px;
border: 1px solid;
}
.left_dummy {
float: left;
width: 100%;
height: 50px;
border: 1px dotted;
}
.right {
float: right;
width: 120px;
height: 40px;
border: 1px solid;
}
</style>
<div class="left">
1
</div>
<div class="right">
2
</div>
<div class="left_dummy"> </div>
<div class="left">
3
</div>
<div class="right">
4
</div>
</body>
</html>