1.行内元素或行内块元素水平居中给其父元素添加text-align:center即可
2.代码：
<!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>块级盒子水平居中对齐</title><style>.header{width: 900px;height: 200px;background-color: pink;margin: 100px auto;text-align: center;}</style></head><body><div class="header"><span>里面的文字</span></div><div class="header"><img src="images/down.jpg" alt=""></div></body></html>
行内元素或行内块元素水平居中给其父元素添加 text-align:center即可
3.运行效果：
