I’m using openSUSE 11.0 with KDE 3.5. The video card is a Nvidia GT series and I’m running Compiz.
After chosing a font to apply to the desktop (Nimbus Sans L) some apps, Firefox for example, do not respect it and use another type or even another size. I’ve also selected GTK apps to use the same font as all the others.
I’ve also installed Okular/KDE4 and everytime I open it the fonts lose the configuration and I need to restart X to put everything normal again.
Firefox responds to the fonts dictated by the author of the website you look at. Where that author doesn’t choose a font, Firefox uses defaults set withing Firefox. The Firefox fontas are adjusted in Edit → Preferences → Content → Fontas and Coliurs
KDE4 is experimental – lots of things don’t work there. To quote the developers:
What to expect of KDE 4.0: 4.0 is the start of KDE 4 and needs testing by the community, that’s why it was released and that’s what you should install it for.
Even so, there might be a way to fix that one – someone might reply with better advice.
Sorry, I’ve not been clear enough: when I talk about the fonts I mean the ones on the menus, toolbars, status bar, …
What I get with Firefox is that the font is usually bigger and of a different type.
There’s a “Force Font” setting for dpi that modifies Ffox. At KDE Personal Settings (Control Centre) → Appearance → Font → Force Font, but that looks pretty limited to me.