title: HTTP headers "q" factor in firefox?
body: <p>Does anyone know what the "q" factor HTTP headers emitted by Firefox 3 mean?</p>
  
  <p>It only appears in the Accept and Accept-Charset headers.</p>
  
  <p>For example:</p>
  
  <p><strong>Accept</strong>: text/html,application/xhtml+xml,application/xml;<strong>q=0.9</strong>,****/****;<strong>q=0.8</strong></p>
  
  <p><strong>Accept-Charset</strong>: ISO-8859-1,utf-8;<strong>q=0.7</strong>,*;<strong>q=0.7</strong></p>
  
  <p>I've tried trawling the web but I haven't quite found the answer.</p>
  
  <p>Is it some sort of weighting, heuristic value or something to do with localization?</p>
  
  <p>Thanks,</p>
  
  <p>Phil'</p>