If you are having trouble using a lesson or tool, try to empty the cache of your browser. You can do this easily by:
1. Pressing 'CTRL-SHIFT-DEL', a pop-up will appear.
2. Just check "Temporary Internet Files", you don't need check the other options.
3. Press the 'Clear browsing data' button.
Some options may look a little different depending on your web browser, however the differences should be minimal. Please contact us at email@example.com if you require further assistance.