Mixed content 是为了安全性而引入的。
在使用https的页面引入了http的内容，此时，称为mixed content。
分为两类：
- Mixed passive/display content
<img>(src attribute)
<video>(src attribute)
<audio>(src attribute)
<object>subresources (when an <object> performs HTTP requests)
- Mixed active content
<script> (src attribute)
<link> (href attribute) (this includes CSS stylesheets)
<iframe> (src attribute)
XMLHttpRequest requests
All cases in CSS where a value is used (@font-face,cursor,background-image, and so forth)
<object> (data attribute)
** Mixed active content 默认被阻塞**
判断依据，是否能修改页面的内容
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[原文地址:https://developer.mozilla.org/en-US/docs/Security/Mixed_content](https://developer.mozilla.org/en-US/docs/Security/Mixed_content)