1. Click the menu button and select Options.
2. Select the Privacy & Security panel.
3. In the Cookies and Site Data section, click Clear Data.
4. Remove the check mark in front of Cookies and Site Data.
5. With Cached Web Content check marked, click the Clear button.
6. Close the about:preferences page. Any changes you’ve made will automatically be saved.

Tip: Here’s another way to clear the Firefox cache:

Click the Library button, click History, and click Clear Recent History…. Next to Time range to clear, choose Everything from the drop-down menu, select Cache in the items list, make sure other items you want to keep are not selected, and then click the Clear Now button.

How to clear cache in Google Chrome 

1. On your computer, open Chrome.
2. At the top right, click More .
3. Click More tools  Clear browsing data.
4. At the top, choose a time range. To delete everything, select All Time.
5. Next to “Cookies and other site data” and “Cached images and files,” check the boxes.
6. Click Clear Data.