How to fix wrong UI views on Firefox

Firefox has a setting to override the web application fonts and style and use a default one,
The result could be the UI elements will look totally wrong like in the following picture.
To fix, please go to FireFox settings:
Tools > Options > Content :

then check the settings: "Fonts & Colors > Advanced: [X] "Allow pages to choose their own fonts"
Quit and restart Fiefox to have the new setting applied.