title: MP4 content type returned as different MIME type in different browsers
body: <p>I have an ASP.NET application built using C# for the backend. I have a form that uploads a pdf and checks the MIME type, application/pdf, to verify it's a valid file. I need to do this on a seperate form for MP4 files but it didn't seem to work. It always returned false. I checked the returned MIME type FileUpload.PostedFile.ContentType in webkit which was perfectly accurate. Firefox 5 and IE 8, however, tested for text/csv and application/octet-stream, respectively. This makes absolutely no sense to me. I also tried mapping extensions to the correct MIME types in the web.config file like so:</p>
  
  <pre><code>&lt;staticContent&gt;
    &lt;mimeMap fileExtension=".mp4" mimeType="video/mp4" /&gt;
    &lt;mimeMap fileExtension=".m4v" mimeType="video/m4v" /&gt;
    &lt;mimeMap fileExtension=".ogg" mimeType="video/ogg" /&gt;
    &lt;mimeMap fileExtension=".ogv" mimeType="video/ogg" /&gt;
    &lt;mimeMap fileExtension=".webm" mimeType="video/webm" /&gt;
  &lt;/staticContent&gt;
  </code></pre>
  
  <p>And in the backend CS file I used this to test the posted file's content type:</p>
  
  <pre><code>if (file.PostedFile.ContentType == "video/mp4" || 
      file.PostedFile.ContentType == "video/mpeg" || 
      file.PostedFile.ContentType == "video/ogg" || 
      file.PostedFile.ContentType == "video/quicktime" || 
      file.PostedFile.ContentType == "video/webm") 
          return true;
  else
          return false;
  </code></pre>
  
  <p>Also please note I am using the local development server that comes with VS</p>