Option 3 for adding MIME types - At the Website Level in IIS7
If you need to add a MIME type for a Web Server that uses IIS7 such Windows 2008 (R2) Server, first of all you should go to Administrative Tools and choose Internet Information Services (IIS) Manager

Click on "MIME Types" IIS Feature.

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Right mouse button click - > Add

Type in the opened window the following:
File name extension: .mp4
MIME type: video/mp4
OK.
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Right mouse button click - > Add

Type in the opened window the following:
File name extension: .webm
MIME type: video/webm
OK.
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Now you can play your .mp4 and .webm videos on the website.
P.S. FLV video format is added to IIS7 by default. In any case the file name extension should be .flv and MIME type: flv-application/octet-stream