Dropdown menu for Fonts

I read in Help :

Fonts Dialog
1.From the Fonts for drop-down list, choose a language group/script. For instance, to set default fonts for the West European languages/scripts (Latin), choose Western. For a language/script not in the list, choose Other Languages.
2.Select whether proportional text should be serif (like "Times New Roman") or sans-serif (like "Arial"). Then specify the font size you want for proportional text.
.../...

I don't find the location of this dropdown list on the Firefox Preferences.
(to improve unpleasant charachters in the Ubuntu Hardy Heron version)