Clearing your web browser's cache, cookies, and history periodically would prevent or resolve performance problems of your computer. Follow these steps to clear your cache on Firefox.
How to Clear Your Cache on Firefox
Step 1: Begin with the "Tools" tab at the top of the page. Then hit "Options" at the dropdown menu.
Step 2: Select the "Privacy & Security" panel.
Step 3: In the "Cached Web Content" section, click "Clear Now".
Step 4: Close the window. Any changes you've made will automatically be saved.