I’ve got more than one gray hair from this one. The symptom is simple: Cassini (the development web server) hosts streaming flash videos just fine. IIS shows a white box.

The answer is annoyingly simple:

1. Open IIS Manager, choose the website.

2. In IIS 7, choose “Mime Types”. In IIS6, right-click, choose properties, choose the HTTP Headers tab, and choose File Types.

3. Click Add. Extension is “.flv” (no quotes), mime type is “video/x-flv” (no quotes)

Not sure if you need to restart the website for changes to take effect. Now hopefully, I’ll remember that next time I’m ready to burn some time trying to figure it out…

source: http://kb.adobe.com/selfservice/viewContent.do?externalId=tn_19439&sliceId=1

source: http://blogs.iis.net/forums/p/1123161/1766940.aspx

source: http://blogs.ittoolbox.com/c/engineering/archives/adding-flv-mime-type-in-iis-4198?e=unrec