FireFox

To Enable JavaScript in Firefox simply:

1. Go to the menu [Tools]-[Options]
2. Select the tab 'Content' at the top of the dialog box which pops up (see image below)
3. Make sure the tick box 'Enable JavaScript' is checked as shown
4. Click [OK]
5. Finally refresh the page [F5] you were viewing to activate the JavaScript within it

Internet Explorer

Enabling JavaScript in Internet Explorer is a little trickier:

1. Select menu [Tools]-[Internet Options] and go to the 'Security' tab at the top of the following pop-up
   
2. Select the zone 'Internet'
3. Click the button [Custom Level] - the following pop-up will appear
   
4. Go down the list of options until you get to [Scripting]-[Active Scripting]
5. Select 'Enable' as shown above
6. Click [OK] to close this pop-up and save the settings
7. Click [OK] to close Internet Options
8. Finally refresh the page [F5] you were viewing to activate the JavaScript within it