This file is returning a MIME type which doesn’t match its content.
What does this mean?
A MIME type defines what a specific file is, and indirectly how it should be handled. For example, a MIME type of
application/x-shockwave-flash signifies an Adobe Flash file.
Sometimes a web server will return incorrect MIME types for certain files, typically when it doesn’t know what those files are. This can cause problems with some browsers or search engines not being able to handle the content consistently.
For example, an HTML webpage could be served with a MIME type of
text/plain. The ‘correct’ way to handle this would be to display the HTML for the page in source form, not the webpage itself. Some browsers would render the page itself, others the source. To avoid this inconsistency, MIME types should be correctly specified.
How do we do this?
You will typically need technical control over your web server; generally this is only possible for dedicated hosting environments.
The default and up-to-date settings for your web server will usually include correct and appropriate MIME types. If you serve non-HTML content via scripts (e.g. generated images) you should ensure your scripts return appropriate MIME headers.