第一种方法：采用绝对定位
<!DOCTYPE>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style>
.one {
position: absolute;
height: 200px;
width: 300px;
background-color: blue;
}
.two {
height: 200px;
margin-left: 300px;
background-color: red;
}
</style>
</head>
<body>
<div class="one"></div>
<div class="two">第一种方法</div>
</body>
</html>
第二种方法：采用左浮动
<!DOCTYPE>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style>
.one {
float:left;
height: 200px;
width: 300px;
background-color: blue;
}
.two {
overflow: auto;
height: 200px;
background-color: red;
}
</style>
</head>
<body>
<div class="one"></div>
<div class="two">第二种方法</div>
</body>
</html>
第三种方法：采用flex布局（推荐使用）
<!DOCTYPE>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width,initial-scale=1,user-scalable=no" />
<title>Document</title>
<style>
*{padding: 0;margin: 0;}
#oo{
display: flex;
flex-wrap: wrap;
}
.one {
float:left;
height: 200px;
width: 200px;
background-color: blue;
}
.two {
background-color: red;
flex: 1;
}
.three{
background-color: pink;
flex: 2;
}
</style>
</head>
<body>
<div id="oo">
<div class="one">1</div>
<div class="two">2</div>
<div class="three">3</div>
</div>
</body>
</html>