I have gtk2.1 working on my system, I know because i have a 2.x theme installed. but when i run ./configure on a nightly build of mozilla i get this message:
checking for GTK - version >= 1.2.0... no
*** The gtk-config script installed by GTK could not be found.
*** If GTK was installed in PREFIX, make sure PREFIX/bin is in
*** your path, or set the GTK_CONFIG environment variable to the
*** full path to gtk-config.
*** GTK+ is available from ftp://ftp.gtk.org/pub/gtk
configure: error: Test for GTK failed
i looked for the file gtk-config but couldn't find it, if it helps i compiled gtk2.1 from source, can anyone help?

it wants gtk not gtk2 you will need to have both libraries installed. this is perfectly fine as they are compeltely seperate to each other, they just were devleoped far apart adn they consequently have substantially different API's. make sure you install the -devel packaege as well if you are using rpms