根据其他的回答，这条消息似乎有很多原因，我想我只是分享我的个人解决方案，以防将来有人有我的确切问题。

Our site loads the CSS files from an AWS Cloudfront distribution, which uses an S3 bucket as the origin. This particular S3 bucket was kept synced to a Linux server running Jenkins. The sync command via s3cmd sets the Content-Type for the S3 object automatically based on what the OS says (presumably based on the file extension). For some reason, in our server, all the types were being set correctly except .css files, which it gave the type text/plain. In S3, when you check the metadata in the properties of a file, you can set the type to whatever you want. Setting it to text/css allowed our site to correctly interpret the files as CSS and load correctly.

当我从谷歌CDN提供的css样式表的css链接中删除协议时，就发生了这种情况。

这不会产生错误:

<link rel="stylesheet" href="//fonts.googleapis.com/css?family=Architects+Daughter">

但是这会给出错误资源解释为样式表，但传输MIME类型text/html:

<link rel="stylesheet" href="fonts.googleapis.com/css?family=Architects+Daughter">

如果你在prod中提供应用程序，请确保你在service worker中提供静态文件。当我在Django上只提供React构建的静态子文件夹时，我遇到了这个错误(没有具有样式的资产)

如果你使用nginx提供静态css，你应该添加

location ~ \.css {
    add_header  Content-Type    text/css;
}
location ~ \.js {
    add_header  Content-Type    application/x-javascript;
}

or

location ~ \.css{
    default_type text/css;
}
location ~ \.js{
    default_type application/x-javascript;
}

到nginx conf

我想从理解问题开始

浏览器向服务器发出HTTP请求。然后服务器做出一个HTTP响应。

请求和响应都由一堆头部和一个(有时是可选的)包含一些内容的主体组成。

如果有一个主体，那么其中一个头是Content-Type，它描述了主体是什么(它是HTML文档吗?一个图像?表单提交的内容?等等)。

当您请求样式表时，服务器会告诉浏览器这是一个HTML文档(Content-Type: text/ HTML)，而不是一个样式表(Content-Type: text/css)。

我已经查过了。Type and text/css已经在css上了。

那么，您的服务器的其他部分使样式表具有错误的内容类型。

使用浏览器开发人员工具的Net选项卡检查请求和响应。

In my case, same error was coming with JSP. This is how I got to the root of this issue: I went to the Network tab and clearly saw that the browser request to fetch the css was returning response header having "Content-type" : "text/html". I opened another tab and manually hit the request to fetch the css. It ended up returning a html log in form. Turns out that my web application had a url mapping for path = / Tomcat servlet entry : (@WebServlet({ "/, /index", }). So, any unmatching request URLs were somehow being matched to / and the corresponding servlet was returning a Log in html form. I fixed it by removing the mapping to /

此外，tomcat配置wrt处理css MIME-TYPE已经存在。