Whenever you get an error installing with yaourt, my first peice of advice would be to try with makepkg then post that output to the forums, as it will generally be much more informative.
In this case, you can just 'cd' to /home/bidar/dev/yaourt/yaourt-tmp-bidar/aur-firefox-kde-opensuse/ then run 'makepkg'. That should provide more useful error information.
]]>adding: hyphenation/hyph_hu.dic (deflated 62%)
Couldn't use given appdir.
make[3]: *** [make-package] Fehler 1
make[3]: Leaving directory `/home/bidar/dev/yaourt/yaourt-tmp-bidar/aur-firefox-kde-opensuse/src/mozilla-release/ff-pgo/browser/installer'
make[2]: *** [default] Fehler 2
make[2]: Leaving directory `/home/bidar/dev/yaourt/yaourt-tmp-bidar/aur-firefox-kde-opensuse/src/mozilla-release/ff-pgo/browser/installer'
make[1]: *** [package] Fehler 2
make[1]: Leaving directory `/home/bidar/dev/yaourt/yaourt-tmp-bidar/aur-firefox-kde-opensuse/src/mozilla-release/ff-pgo'
make: *** [profiledbuild] Fehler 2
I know this post is quite short if there are other informations that were be helpfull ask me please.
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