operaprefs.ini

[Fonts]
EmailCompose=18,4,0,0,0,0,Arial
Email=18,4,0,0,0,0,Arial
HTMLCompose=16,4,0,0,0,0,Arial
PRE=18,4,0,0,0,0,Arial
Form.Text=16,4,0,0,0,0,Arial
Form.Input=14,4,0,0,0,0,Arial
Form.Button=14,4,0,0,0,0,Arial
H4=16,7,0,0,0,0,Arial
H5=13,7,0,0,0,0,Arial
H6=12,7,0,0,0,0,Arial
Prefer Fontconfig Settings=1
Menu=16,4,0,0,0,0,Arial
Toolbar=16,4,0,0,0,0,Arial
Dialog=16,4,0,0,0,0,Arial
Panel=16,4,0,0,0,0,Arial
Tooltip=16,4,0,0,0,0,Arial
Normal=18,4,0,0,0,0,Arial

[CSS Generic Font Family]
Serif=Arial
Sans-Serif=Arial
Cursive=Arial
Fantasy=Arial
Monospace=Arial