Note: Proper font smoothing in Firefox
This setting is key, by default (20) its almost never used.
As I wanted text to be optimized for display quality I set
browser.display.auto_quality_min_font_size = 0
Possible values and their effects
A non-negative integer, specifying device pixels. Text rendered at this size or larger is optimized for display quality rather than display speed. Default is 20.
* Text in chrome (the UI) is always rendered with the high-quality path.
* Web pages can override the effects of this preference by specifying the text-rendering CSS property.
To use the highest quality display and legibility settings for all rendered text, set this preference to 0. Conversely, setting this preference to a very high number will cause Mozilla to use the fastest rendering methods for all text.