You will need to enable Java.
Make sure you have Java installed first (
http://java.sun.com/javase/downloads/index.jsp - Scroll down and select Java Runtime Environment (JRE) 6)
After installing, restart Firefox and IE, whichever browser you installed it on.
For Firefox:
Go to Tools > Options
Select the Content tab. Tick the
Enable Java box. Click OK.
For IE7:
Go to Tools > Internet Options
Select the Advanced tab.
Scroll all the way down till you see Java (Sun)
Tick the
Use JRE 6 for box.
Then select the Security tab.
Click on Internet then Custom Level button.
Scroll all the way down till you see Scripting of Java Applets.
Select Enable. Click OK to apply all settings and restart IE.