firefox

在firefox浏览器中打开: resource://gre-resources/html.css

chrome

https://chromium.googlesource.com/chromium/blink/+/master/Source/core/css/html.css

safari/webkit内核

https://trac.webkit.org/browser/trunk/Source/WebCore/css/html.css

其它

https://zhuanlan.zhihu.com/p/139601700