title: How to check website viewer's operating system?
body: <p>I'm running Ubuntu 8.04 and I recently received the following error when visiting a website:</p>
  
  <blockquote>
    <p>Please return to www.site.com with a computer running Windows 98, 2000, Me, NT, or XP.</p>
  </blockquote>
  
  <ol>
  <li><p>How does the website know which OS I'm running?  Is it only via javascript or is there OS information in the request headers as well?</p></li>
  <li><p>Is there a way for me to bypass this check or "pretend" to be using Windows so that I can access the website even though I'm running an unsupported OS?</p></li>
  </ol>