You may, when using the video embed feature of the HTML editor, encounter an error similar to the following when uploading a video of a supported file type.
This is due to your web server not being configured correctly to deliver files of this extension. You can modify this by adding the appropriate missing MIME types for the required extensions to IIS. If your IIS server is 6.0 see (http://bit.ly/hwalA6) or if your web server is IIS 7.0 or 7.5 see (http://bit.ly/kbkJC6)
The extensions you may be missing are:
Upon adding the appropriate MIME types, please restart the IIS Server service (using IIS Manager) and re-try playing the video. For an in depth list of MIME types, have a look at the following page (http://hosting.com/support/dedicated/iis/mimetypes/)
Here is an example for .mp4: