The MSIE browser maps the file extension of the file belonging to the anchor to an extended description of the file format, which it makes available through the mimeType property. Here is a list of some mimeType values it pays special attention to.
|File type:||MSIE expanded Mime type:|
|.css||Microsoft CSS1 Style Sheet (W3C would have been more appropriate)|
|.htc||Microsoft HTML Component file for behaviors|
|.htm||Microsoft HTML Document 4.0|
|.html||Microsoft HTML Document 4.0|
|.js||Microsoft JScript File (this is a bit presumptuous)|
|.vbs||Microsoft VBScript File|
|.xxx||All unrecognized file types are returned as xxx File with no further expansion|
Microsoft assert that .htm and .html files are "Microsoft HTML" and .css files are "Microsoft CSS1" style sheets. They also assert that .js files are "Microsoft JScript" files. Microsoft don't really own those file extensions across all platforms, nor indeed do they even own them on the Windows platform.
Do not confuse this value with other mimeType properties. For example the Navigator object has a mimeTypes collection property with references to mimeType objects. The mimeType property of an MSIE Anchor object is a simple string primitive value and not a mimeType object.