White/blank squares in Firefox

Currently, the chess board is not compatible with a certain Firefox privacy setting: privacy.resistFingerprinting

This setting is disabled by default but might get enabled when installing Firefox privacy extensions.

It can be disabled again like so:
- go to about:config
- in the search field paste in the name of the setting: privacy.resistFingerprinting
- double-click "privacy.resistFingerprinting" to set its value to false

This should resolve your problem, if not, please get in touch with support.