/*
 * Make all the default font sizes 13 pt:
 */

* {
   font-size: 13pt !important;
}

/*
 * Do not remove the @namespace line -- it's required for correct functioning
 */
@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* set default namespace to XUL */

/* Make all the default font sizes 13 pt. */
* {
    font-family: "Liberation Sans" !important;
    font-size: 13pt !important;
}

''Erykf [[#question-1206659|said]]'' <blockquote> How to change the size of the fonts in the message list, folder list and in emails? Preferences ni works. It's about changing under linux and Kubuntu </blockquote> I suggest you try a setting in preferences. '''[http://kb.mozillazine.org/Menu_differences_in_Windows%2C_Linux%2C_and_Mac Edit|Preferences]'''|Advanced|General→Config Editor Search for ''layout.css.dpi'' and try positive values. -1 means use the system default but if you haven't set the appropriate dpi value in your display settings, that doesn't help much. If that works for you, then fine. Otherwise… Linux users can't use the Theme Font & Size Changer add-on that we recommend for Windows and Mac users, so we have to use the css file method. In my own Linux systems, I find the dpi for the display and set that explicitly in the display settings. Windows and Mac users don't have such a straightforward adjustment; they have to experiment with a slider and some meaningless percentage numbers. Setting that (my dpi is 142) fixes up most display size issues. I use two css files to fine-tune Thunderbird, : ''userContent.css'' sets the message text: /* * Make all the default font sizes 13 pt: */ * { font-size: 13pt !important; } ''userChrome.css'' sets the menus and lists, etc: /* * Do not remove the @namespace line -- it's required for correct functioning */ @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* set default namespace to XUL */ /* Make all the default font sizes 13 pt. */ * { font-family: "Liberation Sans" !important; font-size: 13pt !important; } Obviously, you can change the face and size to suit your own taste and desktop settings.