.: Do you have Java installed on your computer?
  If not, you can download it here.

.: Do you have Java switched on in your browser?
  If not, please turn it on. Review the homesite of your
  browser for more information on how to do that.

.: Does your browser support Java?
  I recommend one of the following browsers:
  Firefox (Windows, MacOS, Linux)
  Opera (Windows, MacOS, Linux)
  Safari (MacOS, Windows)
  Internet Explorer (Windows)