mozilla-firebird-bin ebuild RDEPENDS on =x11-libs/gtk+-2.2* However it works fine with gtk+-2.3 (unstable ebuilds from breakmygentoo) and will most probably work fine with future gtk+-2.4-versions. So it should be changed to >=x11-libs/gtk+-2.2*
As with all binary ebuilds that's difficult to assume until tested.. I'm not really prepared to bump the dependency to 2.3+ based on ebuilds from breakmygentoo.net, either; while I'm sure they work well for most, tracking issues related to non-gentoo ebuilds would become a nightmare. When 2.3 or 2.4 comes into portage proper, this dependency should be re-investigated.
i have gtk-2.4.0 and mozilla-firefox-bin try everytime i sync to restore the old 2.2.4 can someone change the ebuild to ">=x11-libs/gtk+-2.2.4" ? it works fine!