You can specify the default font and size to use; for example:
[Base] ; Font name and size put out at start of file, default none Font=Times Size=3
Not all browsers respect this setting. You can suppress the tag entirely, or omit the face attribute while retaining size:
[HTMLOptions] ; Basefont = Yes (default) or No (no <basefont> tag put out) ; Default is reversed to No if UseCSS=Yes. Basefont = No ; UseFontFace = Yes (default, allow face attrib in font tags) or No UseFontFace = No
If you use CSS, the default value of Basefont is reversed to No; see §31.5 Understanding how CSS affects other options.
If you do not use CSS, and you are not using <font> tags either, you will get whatever fonts a browser specifies as defaults.