Why my Firefox doesn't display Cyrillic fonts well?

[Yuri]

I have this problem for a long time. Firefox shows all Cyrillic fonts 
with very large spaces between letters, almost the same as the real 
space character. So it's very difficult to read. Interestingly, Opera 
shows the same pages very neatly in different font looking very well. I 
attach here fonts section from my xorg.conf.

What's wrong in my configuration?

Yuri


--- fonts section from xorg.conf ---
Section "Files"
        ModulePath   "/usr/local/lib/xorg/modules"
        FontPath     "/usr/local/lib/X11/fonts/misc/"
        FontPath     "/usr/local/lib/X11/fonts/TTF/"
        FontPath     "/usr/local/lib/X11/fonts/OTF"
        FontPath     "/usr/local/lib/X11/fonts/Type1/"
        FontPath     "/usr/local/lib/X11/fonts/100dpi/"
        FontPath     "/usr/local/lib/X11/fonts/75dpi/"
        FontPath   "/usr/local/lib/X11/fonts/TrueType/"
        FontPath     "/usr/local/lib/X11/fonts/tmu/"
        FontPath   "/usr/local/lib/X11/fonts/cyrillic/"
        FontPath  "/usr/local/lib/X11/fonts/dejavu"
EndSection

--- cyrillic fonts installed ---
font-cronyx-cyrillic-1.0.0 X.Org Cronyx Cyrillic font
font-misc-cyrillic-1.0.0 X.Org miscellaneous Cyrillic font
font-screen-cyrillic-1.0.1 X.Org Screen Cyrillic font
font-winitzki-cyrillic-1.0.0 X.Org Winitzki Cyrillic font
xorg-fonts-cyrillic-7.4 X.Org Cyrillic bitmap fonts