Select the “Extras” option from the menu on the bar at the top. Select “Internet options”. Click on the “Security” tab. Click on “Adjust level”. Scroll down to the section with the heading “Scripting”. Select “Activate” from the two “Scripting” options and click on “OK”.
Click on the “Menu” option on the bar at the top, then select “Add-ons”. In the “Add-ons Manager” window, select “Plug-ins”. Click on the Java (TM) platform plug-in (Windows) or the Java applet plug-in (Mac OS X) to select it. Check that the option “Check if it should be activated” or “Always activate” is selected. In older versions of Firefox, click on the “Activate” button instead. (If the Deactivate button is displayed, Java is already activated)