Add MIME mapping in web.config for IIS Express

Putting it in the "web.config" works fine. The problem was that I got the MIME type wrong. Instead of font/x-woff or font/x-font-woff it must be application/font-woff:

<system.webServer>
  ...
  <staticContent>
    <remove fileExtension=".woff" />
    <mimeMap fileExtension=".woff" mimeType="application/font-woff" />
  </staticContent>
</system.webServer>

See also this answer regarding the MIME type: https://stackoverflow.com/a/5142316/135441

Update 4/10/2013

Spec is now a recommendation and the MIME type is officially: application/font-woff

If anybody encounters this with errors like Error: cannot add duplicate collection entry of type ‘mimeMap’ with unique key attribute and/or other scripts stop working when doing this fix, it might help to remove it first like this:

<staticContent>
  <remove fileExtension=".woff" />
  <mimeMap fileExtension=".woff" mimeType="application/font-woff" />
</staticContent>

At least that solved my problem

<system.webServer>
     <staticContent>
      <remove fileExtension=".woff"/>
      <mimeMap fileExtension=".woff" mimeType="application/font-woff" />
      <mimeMap fileExtension=".woff2" mimeType="font/woff2" />
    </staticContent>
  </system.webServer>