Start by pressing Ctrl + Shift + Del, or clicking the 3 dots in the top right corner of the screen, going to More tools, and clicking Clear browsing data.
A new tab will open showing the following screen:
Change the dropdown from the past hour to the beginning of time, and check the Cached images and files box as well as the Hosted app data box.
Click the Clear Browsing Data button and you're done! Restart Chrome and the issue should be fixed.
First, click the menu button in the top right corner of the screen, and click Options.
On the Options tab, click the Advanced tab on the left and click on Network
Finally, click Clear Now.
Restart Firefox and your issue should be fixed!