The Tor Browser / file revision

 <script>

 /*

  * Almost all of the image decoding reftests require the display to be in

  * 24-bit color mode, or else the rendered images will have subtle color

  * variations and will fail.

  * The Windows test boxes used to have a tendency to flip to 16-bit color mode,

  * so this test will explicitly check the color depth to make it more obvious

  * when the requirement is not met. (See bug 414720.)

  * 24-bit is only a minimum, allow higher values too. (See bug 458847.)

  */

 var colorDepth = window.screen.colorDepth;

 if (colorDepth < 24)

     document.write("ERROR: color depth is only " + colorDepth + ".");

 </script>