title: Page displays random symbols instead of error message on Firefox
body: <p>Randomly, on a few projects, some pages display random symbols instead of an error message. Like this one :</p>
  
  <p>��������<code>I�%&amp;/m�{J�J��t��</code>$@�����iG#)�*��eVe]f@�흼 ��{���{��;�N'���?\fdl��J�ɞ!���?~|?"��Ey�')=��y6����h�����Ųi��- �ez����7i޴i�L���,�4�̧i���Ίe��Ͼ|uz����:�}�<em>��U{���������΋��~�ȗu.-�����l>F'�����Y�l��$k�tF����</em>��{�� ��[����'U���|6J�lR��b6��юG�k�^,ӏ��߿�}&lt;~&lt;�;c�R鱕iV��m�|��� �yDl���tRͮ�<em>|N��>�Ey�裟�k</em>��!z���Ѳ�Y)5��G��A�8$D��Ѥ̦oI��]�P �"�/��v[����W�~���m`N�rvk���Mqz3���wV�</p>
  
  <p>It happens quite randomly, and seems to be caused by different factors. Here, it's on a file upload.</p>
  
  <p>We use SharpZipLib on this page, but the codepath shouldn't use it.</p>
  
  <p>Does anyone knows why this happens, and how to prevent it ?</p>
  
  <p><strong>EDIT :</strong> it only happens on Firefox. IE(8) displays the error message correctly.</p>
  
  <p><strong>EDIT 2 :</strong> it seems to happen quite randomly, only on some pages/sites. The same page on another IIS site works well. It seems to do this only on IIS7 ; I have no reports of those on IIS6, and I haven't encountered it on my dev machine.</p>
  
  <p><strong>EDIT 3 :</strong> it looks like it happens only when the page crashes.</p>
  
  <p><strong>EDIT 4 :</strong> Ok, so, it happens only on IIS7, and only when I get an error 500. I think it might be the IIS error pages that have a problem. How can I try to change them ?</p>
  
  <p>Firebug gives me those headers :</p>
  
  <p><em>Response</em><br>
  Cache-Control   private<br>
  Content-Type    text/html; charset=utf-8<br>
  Server  Microsoft-IIS/7.0<br>
  X-AspNet-Version    2.0.50727<br>
  X-Powered-By    ASP.NET<br>
  Date    Mon, 04 Apr 2011 10:31:24 GMT<br>
  Content-Length  2284<br>
  <em>Request</em><br>
  Host    xxxx<br>
  User-Agent  Mozilla/5.0 (Windows; U; Windows NT 6.1; fr; rv:1.9.2.16) Gecko/20110319 Firefox/3.6.16 ( .NET CLR 3.5.30729; .NET4.0E)<br>
  Accept  text/html,application/xhtml+xml,application/xml;q=0.9,<em>/</em>;q=0.8<br>
  Accept-Language fr,fr-fr;q=0.8,en-us;q=0.5,en;q=0.3<br>
  Accept-Encoding gzip,deflate<br>
  Accept-Charset  ISO-8859-1,utf-8;q=0.7,*;q=0.7<br>
  Keep-Alive  115<br>
  Connection  keep-alive<br>
  Referer xxxxx<br>
  Cookie  xxxxxx</p>
  
  <p>Is there any way for me to say "on this page, I don't accept gzip compression at all" ?</p>