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border-image-repeat border-image-slice border-image-source border-image-width border-inline border-inline-color border-inline-end border-inline-end-color border-inline-end-style border-inline-end-width border-inline-start border-inline-start-color border-inline-start-style border-inline-start-width border-inline-style border-inline-width border-left border-left-color border-left-style border-left-width border-radius border-right border-right-color border-right-style border-right-width border-spacing border-start-end-radius border-start-start-radius border-style border-top border-top-color border-top-left-radius border-top-right-radius border-top-style border-top-width border-width bottom box-decoration-break box-reflect box-shadow box-sizing break-after break-before break-inside caption-side caret-color @charset 规则 clear clip clip-path color color-scheme column-count column-fill column-gap column-rule column-rule-color column-rule-style column-rule-width column-span column-width 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布局 - width 和 max-width

阅读1042

更新时间2025-07-16

布局 - z-index

使用 width、max-width 和 margin: auto;

如上一章所述，块级元素始终占用可用的全部宽度（尽可能向左和向右伸展）。

设置块级元素的 width 将防止其延伸到其容器的边缘。然后，您可以将外边距设置为 auto，以将元素在其容器中水平居中。元素将占用指定的宽度，剩余空间将在两个外边距之间平均分配：

这个

元素的宽度为 500px，外边距设置为 auto。

注意：当浏览器窗口小于元素的宽度时，上面这个

会发生问题。浏览器会将水平滚动条添加到页面。

在这种情况下，使用 max-width 可以改善浏览器对小窗口的处理。为了使网站在小型设备上可用，这一点很重要：

这个

元素的最大宽度为 500px，外边距设置为 auto。

提示：请将浏览器窗口的大小调整为小于 500 像素，以查看两个 div 之间的区别！

这是上面两个 div 的例子：

实例

div.ex1 {
  width: 500px;
  margin: auto;
  border: 3px solid #73AD21;
}

div.ex2 {
  max-width: 500px;
  margin: auto;
  border: 3px solid #73AD21;
}

运行实例 »

点击 "运行实例" 按钮查看在线实例

布局 - z-index