Summary
- The
htmlandbodyelements are distinct block-level entities, in a parent/child relationship. - The
htmlelement’s height and width are controlled by the browser window. - It is the
htmlelement which has (by default)overflow:auto, causing scrollbars to appear when needed. - The
bodyelement is (by default)position:static, which means that positioned children of it are positioned relative to thehtmlelement’s coordinate system. - In almost all modern browsers, the built-in offset from the edge of the page is applied through a
marginon thebodyelement, notpaddingon thehtmlelement.
重要的一点：html 的宽和高 由浏览器窗口控制
block-level elements which don’t have a specific height applied to themautomatically grow in height to accommodate their content. What happens when a height is applied? It depends on the value of the CSS overflow property
块级元素默认没有特别指定高度，根据包裹其中的内容自动增长高度，如果为其指定高度，接下来发生的事就要取决于 overflow 这个属性的值了。
html 元素 默认 overflow 熟悉为 auto，但是没有指定它的高，为什么会出现scrollbar？
The html element is a little bit special. Its height and width are governed by the window/frame it’s in. When you increase your window width, the fixed width of the html element is increased; when you make the window taller, so increases the height of the html element.
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