title: File Upload with RegularExpressionValidator not working with Firefox only IE
body: <p>I have a FileUpload with a RegularExpressionValidator with the following Validation Expression:</p>
  
  <pre><code>^(([a-zA-Z]:)|(\\{2}\w+)\$?)(\\(\w[\w].*))+(.gif|.jpg|.JPG|.JPEG|.GIF|.jpeg|.png|.bmp|.3dm|.3dmf|.ai|.drw|.dxf|.esp|.mng|.png|.ps|.psp|.svg|.tiff)$
  </code></pre>
  
  <p>This way I make sure the User only upload images.
  But for some reason it does not work when I use Firefox. Why is that and how can I go around the problem?</p>