In the address bar, type about:config and press Enter
Click 'I'll be careful, I promise' or 'I'm over 18 and can think for myself' if a warning message appears
Mozilla Firefox - Version lower than v23
On the web browser menu click 'Tools' and select 'Options'
In the 'Options' window select the 'Content' tab
In the opened 'Options' window click on the 'OK' button to close it
Click on the 'Reload current page' button of the web browser to refresh the page