Incorrect MIME Type for CSS Files

Tristan Nitot, Netscape Communications

Published 18 Mar 2002 (Feedback)

What is the problem?

You may come across a web page using CSS with poor layout with Netscape 7.x or any Gecko-based browser such as Mozilla, while MSIE displays it nicely. One of the common reasons for this is an improper configuration of the web server hosting the CSS file. Some Apache and iPlanet web servers are associating files having a .CSS with an incorrect MIME-type such as "text/plain" or "text/x-pointplus". In some cases, Netscape 7.x and Mozilla ignore the CSS file because of its wrong MIME type and use a default style sheet that causes the layout to be different from what was intended by the web developer.

When does this happen?

The W3C specification mentions that CSS files should be served with a "text/css" MIME type. Mozilla and Netscape 7.x, when used in "strict mode" will follow the specification closely and expect the CSS file to be served with a correct MIME type ("Strict mode" is enabled by having a strict DTD mentioned in the first line of the HTML page). In "quirks mode", both application will tolerate the wrong MIME type and use the attached style sheet despite the incorrect server configuration. This means that you cannot have "Strict" documents with a misconfigured server. MSIE lets you get away with this misconfiguration by incorrectly not taking care of the MIME type provided by the server in the http header.

What can I do to change this?

You must ask the server administrator to update the MIME type configuration file for the web server.
This issue, for iPlanet/Netscape web servers has already been acknowledge by the vendor, who has issued a tech note in its knowledge base.

If you use Apache, you could also change configuration of the .htaccess file in your root directory (The .htaccess file is a read-only configuration file that handles a few things including MIME types.). Add this line to your .htaccess file:

AddType text/css .css

Please note that some Webmasters disable the use of .htaccess configuration file on their Apache server because it has a small performance hit.

Conclusion

Using a strict document type definition with Mozilla means that the web server that serves your web pages needs to be configured appropriately. There are several workarounds to this problem, but the most effective is to have the correct MIME type associated with .css files. Ask the Webmaster to fix this for you, all everybody publishing html documents with strict DTDs will thank you!