Title is written on 2 lines with Ubuntu Firefox and doesn't fit menu bar, is it me or is it a serious bug?
I wouldn't consider this a serious bug, but it certainly is a bug, and it's worth reporting as one.
Text in the title bar should not be cut off at the top and the bottom, which is what is happening here as a result of two lines being crammed into a space that can only fit one.
This bug should be reported against
firefox in Ubuntu, using Apport. See these resources for details:
When reporting the bug, please make sure to provide details about how to reproduce the problem, state specifically what is happening that shouldn't be (or what isn't happening that you think should), and attach a screenshot to the bug report on Launchpad. Apport will send data about your Firefox installation to Launchpad, where you'll fill out a bug report, as explained in the above two resources.