[Fontconfig] Font size depends on screen?

[Marius Schaefer/Camberg/ISBAC]

Hello, 

Don't know whether this is the right list. I've got a strange problem. I'm 
running X.org to display some html files using mozilla running in 
fullscreen mode at 848x480. On some displays it looks very well, but on 
some (16/9 plasma) screens the fonts are displayed too big while other 
html elements (tables, ...) are correct. This looks quite bad.
On a 17" crt screen the output is correct. On a 19" crt it's broken. I 
also tested a 17" 16/9 tft and two 16/9 plasma screens where the fonts 
were too big.
The 19" crt and both plasma screens don't provide any ddc information, 
while the 17" tft and the 17" crt have ddc information. I also have 
'Option "NoDDC"' in my xorg.conf to be able to set a resolution like 
848x480 on all screens. 

I don't know what causes this problem, maybe someone can help me?

Thanks
Marius Schäfer