#DD{ position: relative; top: 0px; left: 0px; width: 500px; height: 300px; overflow: hidden;}#A1{ position: relative; width: 100%; height: 100%; padding-bottom: 50px; background-color: #F00;}#A2{ position: relative; width: 100%; height: 100%; border-bottom: solid 50px #000000; background-color: #F00;}#B{ position: relative; top: 0px; left: 0px; width: 100%; height: 100%; overflow-x:hidden; overflow-y:auto; background-color: #00F;}<html><head><link rel="stylesheet" href="css.css" type="text/css"></head><body><div id="DD"> <span id="A1"> <span id="B"> <ul> <li>1</li> <li>1</li> <li>1</li> <li>1</li> <li>1</li> <li>1</li> <li>1</li> <li>1</li> <li>1</li> <li>1</li> <li>1</li> <li>1</li> <li>1</li> <li>1</li> <li>1</li> <li>1</li> <li>1</li> <li>1</li> <li>1</li> <li>1</li> </ul> </span> </span></div></body></html>
页面刚打开是不对的，但是切换一下页面又对了
把span标签换成div，span是内联元素，不能定义block元素的属性
![[Web front-end] Démarrage rapide de Node.js](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
