In order to resolve an issue you are having, you need to know how to delete the Firefox cache / history files from the browser.
Click the menu button and choose Options.
Select the Advanced panel.
Click on the Network tab.
In the Cached Web Content section, click Clear Now.
5. Close the about:preferences page. Any changes you've made will automatically be saved.
1. Click the menu button, as shown above, and choose History.
2. Select Clear Recent History
3. Select "Everything" for the time range, and check Cookies and Cache. Click Clear now.