我也有这个错误的问题，并想出了一个解决方案。这并没有解释错误发生的原因，但似乎在某些情况下修复了它。

在css文件的路径前加上一个正斜杠/，如下所示:

<link rel=“stylesheet” href=“/css/bootstrap.min.css”>

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

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.

I faced the same issue while configuring Postfix Admin 3.2. According to the official documentation, the whole Postfix Admin content should be extracted into a separate directory, i.e. /srv/postfixadmin and not the document root. Only the /srv/postfixadmin/public directory should be symlinked into /var/www/html document root. I have just extracted the whole content into /var/www/html. Having played with Nginx server block settings, I managed example.com/postfixadmin resolving from /var/www/html/postfixadmin/public. Nevertheless, images and CSS were not available with 404 status code. The stylesheets were broken. I got the error message OP quoted with respective 404 entries in access log.

在我的情况下，我只是移动/var/www/html/postfixadmin到/srv/postfixadmin和ln -s /srv/postfixadmin/公共/var/www/html/postfixadmin。这完全解决了问题。 这是参考资料。

我在恢复一个旧的MEAN堆栈项目时遇到了同样的问题。我使用nodemon作为我的本地开发服务器，得到了相同的错误资源解释为样式表，但使用MIME类型text/html传输。我从nodemon更改为http-server，可以在这里找到。它立刻对我起了作用。