The following warning printed by the firefox 3.0 ebuild isn't very meaningful: All the packages built against mozilla-firefox won't compile, if after installing firefox 3.0 you get some blockers, please add 'xulrunner' to your USE-flags. Suggest changing it to something like this: The UI and rendering libraries that were part of the mozilla-firefox 2.x package have been split from the mozilla-firefox 3.x package and are now in the xulrunner package. In order for ebuilds to use xulrunner instead of mozilla-firefox 2.x, the "firefox" USE flag must be replaced by the "xulrunner" USE flag. Failure to replace the "firefox" USE flag with the "xulrunner" USE flag will result in portage attempting to merge mozilla-firefox 2.x which is incompatible with mozilla-firefox 3.x and will block some packages from building. Reproducible: Always
I suggest shorter wording: With Firefox 3 "xulrunner" is used instead of the "firefox" USE flag. Failure to change your USE flags may result in portage attempting to merge mozilla-firefox 2.x - this is incompatible with mozilla-firefox 3.x and will block some packages from building. Or even shorter: Welcome to Firefox 3! If you have "firefox" in your USE flags, please change it to "xulrunner".
Well, now that 3.5 is out, this bug is really obsolete... Marking as WONTFIX...
This bug is still biting. One month after marked WONTFIX, 3.5 still isn't stable.