1、左右两个div都设置为float:left，如果右边div没有设置宽度，右边div的宽度会根据div里的内容自动调整。
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"
/>
<title>无标题文档</title>
<style type="text/css">
* { margin: 0; padding:0;}
.left {
float:
left;
width: 200px;
height: 200px;
background:#009966;
}
.right {
height: 200px;
background: #FF6633;
float:left;
}
</style>
</head>
<body>
<div class="left">I am left</div>
<div class="right">I am right</div>
</body>
</html>
2、只有左侧div设置为float:left，右侧div设置overflow:auto;，右侧div将会占据整个右侧剩余宽度。
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"
/>
<title>无标题文档</title>
<style type="text/css">
* { margin: 0; padding:0;}
.left {
float:
left;
width: 200px;
height: 200px;
background:#009966;
}
.right {
height: 200px;
background: #FF6633;
overflow:auto;
}
</style>
</head>
<body>
<div class="left">I am left</div>
<div class="right">I am right</div>
</body>
</html>
3、两个div都设置为display:
inline-block;这样可能会出现两个div顶端不对齐的情况，可以在右侧div设置vertical-align: top;
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"
/>
<title>无标题文档</title>
<style type="text/css">
* { margin: 0; padding:0;}
.left {
display:
inline-block;
width: 200px;
height: 200px;
background:#009966;
}
.right {
height: 200px;
background: #FF6633;
display:
inline-block;
vertical-align: top; //与左侧div顶部对齐
}
</style>
</head>
<body>
<div class="left">I am left</div>
<div class="right">I am right</div>
</body>
</html>
两个div横向排列，顶端对齐的方式。