Each file fetched through a web server contains a MIME content type that identifies what type of file it is. Thus an HTML file has the content type text/html, while a GIF image has the content type image/gif.

On a Challenger server, the file extension determines the content type of that file. Usually .html or .htm files are given the content type text/html while .gif files are given the content type image/gif.

As a user, you usually don't have to bother with content types. If you just give your files their standard extensions everything will work. But sometimes, when you try out new plugins that use their own file format, the extension and content type that you want to use is not handled by the server. Then the administrator for the server has to change the configurations for the Content types module.

Some extensions might be handled by the web server itself. The most common use is to run files through the Main RXML parser module. This makes it possible to use RXML tags on such pages. Depending on the policy of your site this might be done for all .html files, or only for special .rxml files.