尝试一下》

          <!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <style>
    #myDIV {
      width: 500px;
      background-color: lightblue;
      overflow: auto;
      border: 1px solid black;
      -webkit-animation: mymove 5s infinite;
      /* Chrome, Safari, Opera */
      animation: mymove 5s infinite;
    }
    /* Chrome, Safari, Opera */

    @-webkit-keyframes mymove {
      50% {
        min-height: 400px;
      }
    }
    /* Standard syntax */

    @keyframes mymove {
      50% {
        min-height: 400px;
      }
    }
  </style>
</head>
<body>

  <p>逐步改变 max-height, 从 "none" 到 "400px":
    <p>
      <div id="myDIV">
        <p>This DIV element does not have a pre-defined height.</p>
        <p>An animation will change the min-height, from "none" to "400px".</p>
      </div>

      <p>min-height 属性支持动画效果。</p>
      <p><b>注意：</b>Internet Explorer 9 及更早 IE 版本不支持 CSS 动画。</p>

</body>
</html>
        
尝试一下 》
