You can also specify which font to use on the invocation of a window:
xrsh cs xterm -font courb14
Or you can permanently change your default fonts by putting an entry in your .Xdefaults file
*font: *-courier-bold-r-normal-*-*-140-* *Font: *-courier-bold-r-normal-*-*-140-*and making sure the xrdb line is uncommented in your .xinitrc file.
Fonts under netscape are controlled via [Edit] => Preferences. Under Appearance, select Fonts. There you can choose what font to and size use for both variable and fixed width fonts.