title: Firefox and SSL: sec_error_unknown_issuer
body: <p>My client gets a <code>sec_error_unknown_issuer</code> error message when visiting <a href="https://mediant.ipmail.nl" rel="noreferrer">https://mediant.ipmail.nl</a> with Firefox.
  I can't reproduce the error myself. I installed FF on a Vista and a XP machine and had no problems. FF on Ubuntu also works fine.</p>
  
  <p>Does anyone get the same error and does anyone have some clues for me so I can tell my ISP to change some settings?
  The certificate is a so called wild-card SSL certificate that works for all subdomains (*.ipmail.nl). Was I wrong to pick the cheapest one?</p>