I really hope it's not diffrence in each version of linux... or there is a function that I can find where it is? sorry for all those stupid questions :) Thanks.

Well there's not necessarily one specific directory and it could be different depending on your particular setup. One way to find out is to open up your X config (either /etc/X11/XF86Config or /etc/X11/xorg.conf) and look for lines that say:

FontPath "<some directory>"

where those directories are your font directories. On the other hand you might just have one entry saying comething like:

FontPath "unix/:-1"

or

FontPath "unix/:7100"

in which case you are using a font server and your font directories will be specified in another file. If you are using xfs (X Font Server, not the filesystem) the config might be in /etc/X11/fs/config which has an entry called "catalogue" that lists all your font directories.

BTW, why do you want to know where the font directories are? So you can add new fonts? Google can usually tell you how to do that...