为什么需要浮动

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什么是浮动

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  1. <!DOCTYPE html>
  2. <html lang="en">
  4. <head>
  5.   <meta charset="UTF-8">
  6.   <meta http-equiv="X-UA-Compatible" content="IE=edge">
  7.   <meta name="viewport" content="width=device-width, initial-scale=1.0">
  8.   <title>Document</title>
  10.   <style>
  11.     .one,
  12.     .two {
  13.       width: 100px;
  14.       height: 100px;
  15.       background-color: blue;
  16.       float: left;
  17.     }
  19.     .two {
  20.       float: right;
  21.     }
  22.   </style>
  23. </head>
  25. <body>
  26.   <div class="one"></div>
  27.   <div class="two"></div>
  28. </body>
  30. </html>

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浮动特性（重难点）

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1浮动元素会脱离标准流（脱标）

视频：https://www.bilibili.com/video/BV1pE411q7FU?p=173
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  1. <!DOCTYPE html>
  2. <html lang="en">
  4. <head>
  5.   <meta charset="UTF-8">
  6.   <meta http-equiv="X-UA-Compatible" content="IE=edge">
  7.   <meta name="viewport" content="width=device-width, initial-scale=1.0">
  8.   <title>Document</title>
  10.   <style>
  11.     .one {
  12.       width: 100px;
  13.       height: 100px;
  14.       background-color: blue;
  15.       float: left;
  16.     }
  18.     .two {
  19.       width: 200px;
  20.       height: 200px;
  21.       background-color: red;
  22.     }
  23.   </style>
  24. </head>
  26. <body>
  27.   <div class="one">浮动</div>
  28.   <div class="two">标准流</div>
  29. </body>
  31. </html>

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2.浮动的元素会一行内显示并且元素顶部对齐

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<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>

  <style>
    div {
      width: 300px;
      height: 300px;
      float: left;
      background-color: blue;
    }

    .two,
    .four {
      background-color: red;
    }

    .two {
      height: 400px;
    }
  </style>
</head>

<body>
  <div class="one">1</div>
  <div class="two">2</div>
  <div class="three">3</div>
  <div class="four">4</div>
</body>

</html>

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当我缩小浏览器时
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3.浮动元素会具有行内块元素特性

视频：https://www.bilibili.com/video/BV1pE411q7FU?p=175&spm_id_from=pageDriver
image.png

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>

  <style>
    span {
      width: 100px;
      height: 100px;
      background-color: blue;
      float: left;
    }

    div {
      height: 200px;
      background-color: red;
      float: right;
    }
  </style>
</head>

<body>
  <span></span>
  <div>111111</div>
</body>

</html>

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浮动元素经常和标准流父级搭配使用

视频：https://www.bilibili.com/video/BV1pE411q7FU?p=176
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解决这样的布局。image.png

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>

  <style>
    .father {
      width: 600px;
      height: 100px;
      background-color: rgb(134, 115, 115);
      margin: 100px auto;
    }

    .father div {
      width: 100px;
      height: 100px;
      background-color: blue;
      float: left;
    }
  </style>
</head>

<body>
  <div class="father">
    <div>1</div>
    <div>2</div>
    <div>3</div>
  </div>
</body>

</html>

效果图
image.png