You need a Java-enabled web browser with Java Runtime Environment (JRE) installed.
Try downloading a free JRE click here.
If installing JRE and restarting your computer didn't work,
check that Java is enabled in I.E. (Microsoft Internet Explorer).
Go to: Tools/Internet Options.../Advanced. Under Java, click Use Java.
If you don't use I.E. I highly recommend it.
To download I.E. (windows only) click here.