This also ought to work for the Chrome browser.

These instructions are intended to restore the use of websites that are currently not working due to some sort of data stored in your web browser data cache.

WARNING: This will potentially delete the following sort of things: such as settings for websites you may have visited, saved logins and passwords, saved payment credentials, credit cards and the such, maybe other things too.  It’s all data that you can probably enter in again but clearing your web browser cache is arguably destructive and could cause you some inconveniences.

Chromium

Menu -> More tools -> Clear browsing data… -> Advanced

Time range: All time

Select all the checkboxes; then, click the “Clear data” button.

Firefox

Menu -> History -> Clear recent history…

Time range to clear: Everything

Select all the checkboxes; then, click the ‘OK’ button.

Chromium, Screenshots

Pic 1:

Chromium - Clear Browser Cache - Frame 1

 

Pic 2:

Chromium - Clear Browser Cache - Frame 2

Firefox, Screenshots

Pic 1:

Firefox - Clear Browser Cache - Frame 1

 

Pic 2:

Firefox - Clear Browser Cache - Frame 2

 

Pic 3:

Firefox - Clear Browser Cache - Frame 3