Changing the banner font

[Ivivanti]

Hi -

How do I change the font for my banners? I've used Notepad to go into the
_vti... directories and changed the font in the .css files there from the
displayed font to my desired font, but after I save those files and open
them again the font values keep changing back to the previous values.

Is there a simpler way to do this?

Thanks,
Ivi